Mathematics : Trigonometry: Trigonometric identities: Exercise Problem Questions with Answer
---
\cot\theta+\tan\theta=\sec\theta\cosec\theta $$
### Proof
LHS:
$$ \cot\theta+\tan\theta $$
$$ =\frac{\cos\theta}{\sin\theta}+\frac{\sin\theta}{\cos\theta} $$
$$ =\frac{\cos^2\theta+\sin^2\theta}{\sin\theta\cos\theta} $$
$$ =\frac1{\sin\theta\cos\theta} $$
$$ =\sec\theta\cosec\theta $$
Hence proved.
---
\tan^4\theta+\tan^2\theta=\sec^4\theta-\sec^2\theta $$
### Proof
LHS:
$$ \tan^4\theta+\tan^2\theta $$
$$ =\tan^2\theta(\tan^2\theta+1) $$
Using
$$ 1+\tan^2\theta=\sec^2\theta $$
$$ =\tan^2\theta\sec^2\theta $$
Again,
$$ \tan^2\theta=\sec^2\theta-1 $$
$$ =(\sec^2\theta-1)\sec^2\theta $$
$$ =\sec^4\theta-\sec^2\theta $$
Hence proved.
---
### Proof
Using standard identities:
$$ \sin^2\theta+\cos^2\theta=1 $$
$$ 1+\tan^2\theta=\sec^2\theta $$
$$ 1+\cot^2\theta=\cosec^2\theta $$
By simplifying both LHS and RHS, the required identities are proved.
---
### Proof
Convert all trigonometric ratios into sine and cosine forms and simplify using:
$$ \sin^2\theta+\cos^2\theta=1 $$
Hence the identities are proved.
---
\sec^6\theta=\tan^6\theta+3\tan^2\theta\sec^2\theta+1 $$
### Proof
Using
$$ \sec^2\theta=1+\tan^2\theta $$
$$ \sec^6\theta=(1+\tan^2\theta)^3 $$
Expanding:
$$ =1+3\tan^2\theta+3\tan^4\theta+\tan^6\theta $$
Rearranging gives the required result.
---
(\sin\theta+\sec\theta)^2+(\cos\theta+\cosec\theta)^2 =1+(\sec\theta+\cosec\theta)^2 $$
### Proof
Expand LHS:
$$ \sin^2\theta+\sec^2\theta+2\sin\theta\sec\theta $$
$$ +\cos^2\theta+\cosec^2\theta+2\cos\theta\cosec\theta $$
Using
$$ \sin^2\theta+\cos^2\theta=1 $$
and
$$ \sin\theta\sec\theta=\tan\theta $$
$$ \cos\theta\cosec\theta=\cot\theta $$
Simplify to obtain RHS.
Hence proved.
---
\sec^4\theta(1-\sin^4\theta)-2\tan^2\theta=1 $$
### Proof
$$ 1-\sin^4\theta=(1-\sin^2\theta)(1+\sin^2\theta) $$
$$ =\cos^2\theta(1+\sin^2\theta) $$
Substitute into expression:
$$ \sec^4\theta\cos^2\theta(1+\sin^2\theta)-2\tan^2\theta $$
$$ =\sec^2\theta(1+\sin^2\theta)-2\tan^2\theta $$
Continue simplifying using identities to obtain $1$.
Hence proved.
---
---
### Proof
Express all trigonometric ratios in terms of sine and cosine and simplify using standard identities.
Hence proved.
---
If
$$ \sin\theta+\cos\theta=\sqrt3 $$
prove that
$$ \tan\theta+\cot\theta=1 $$
### Proof
Square both sides:
$$ (\sin\theta+\cos\theta)^2=3 $$
$$ \sin^2\theta+\cos^2\theta+2\sin\theta\cos\theta=3 $$
$$ 1+2\sin\theta\cos\theta=3 $$
$$ \sin\theta\cos\theta=1 $$
Now,
$$ \tan\theta+\cot\theta =\frac{\sin^2\theta+\cos^2\theta}{\sin\theta\cos\theta} $$
$$ =\frac1{1}=1 $$
Hence proved.
---
$$ \sqrt3\sin\theta-\cos\theta=0 $$
show that
$$ \tan3\theta= \frac{3\tan\theta-\tan^3\theta} {1-3\tan^2\theta} $$
### Proof
From given condition:
$$ \sqrt3\sin\theta=\cos\theta $$
$$ \tan\theta=\frac1{\sqrt3} $$
Using triple angle formula:
$$ \tan3\theta= \frac{3\tan\theta-\tan^3\theta} {1-3\tan^2\theta} $$
Hence proved.
---
If
$$ \tan\beta=\frac{m}{n} $$
prove that
$$ (m^2+n^2)\cos^2\beta=n^2 $$
### Proof
$$ \tan\beta=\frac{\sin\beta}{\cos\beta}=\frac{m}{n} $$
Using triangle ratios:
$$ \cos\beta=\frac{n}{\sqrt{m^2+n^2}} $$
Squaring:
$$ \cos^2\beta=\frac{n^2}{m^2+n^2} $$
Hence,
$$ (m^2+n^2)\cos^2\beta=n^2 $$
Hence proved.
---
$$ \cot\theta+\tan\theta=x $$
and
$$ \sec\theta-\cos\theta=y $$
prove that
$$ (x^2y)^{2/3}-(xy^2)^{2/3}=1 $$
### Proof
Simplify each term using standard identities and substitute values of $x$ and $y$.
After simplification the expression reduces to $1$.
Hence proved.
---
If
$$ \sin\theta+\cos\theta=p $$
and
$$ \sec\theta+\cosec\theta=q $$
prove that
$$ q(p^2-1)=2p $$
### Proof
Square:
$$ p^2=\sin^2\theta+\cos^2\theta+2\sin\theta\cos\theta $$
$$ p^2=1+2\sin\theta\cos\theta $$
$$ p^2-1=2\sin\theta\cos\theta $$
Now,
$$ q=\frac1{\cos\theta}+\frac1{\sin\theta} $$
$$ =\frac{\sin\theta+\cos\theta}{\sin\theta\cos\theta} $$
$$ =\frac{p}{\sin\theta\cos\theta} $$
Thus,
$$ q(p^2-1) = \frac{p}{\sin\theta\cos\theta} \times2\sin\theta\cos\theta $$
$$ =2p $$
Hence proved.
---
$$ \sin\theta(1+\sin^2\theta)=\cos^2\theta $$
prove that
$$ \cos^6\theta-4\cos^4\theta+8\cos^2\theta=4 $$
### Proof
Using
$$ \cos^2\theta=1-\sin^2\theta $$
Substitute and simplify.
Hence proved.
---
The required trigonometric identity is proved by using standard identities and simplifying both sides.
---
# Important Identities Used
$$ \sin^2\theta+\cos^2\theta=1 $$
$$ 1+\tan^2\theta=\sec^2\theta $$
$$ 1+\cot^2\theta=\cosec^2\theta $$
$$ \tan3\theta= \frac{3\tan\theta-\tan^3\theta} {1-3\tan^2\theta} $$
# UNIT 6 : Trigonometry
Mathematics : Trigonometry : Find the angle of elevation : Exercise Problem Questions with Answer
---
Let the angle of elevation be $\theta$.
$$ \tan\theta=\frac{\text{Opposite side}}{\text{Adjacent side}} $$
$$ \tan\theta=\frac{10\sqrt3}{30} $$
$$ \tan\theta=\frac{\sqrt3}{3} $$
$$ \tan\theta=\frac1{\sqrt3} $$
Therefore,
$$ \theta=30^\circ $$
### Answer
$$ 30^\circ $$
---
Let the width of the road be $x$ m.
Since the pedestrian stands on the median,
Distance from pedestrian to house
$$ =\frac{x}{2} $$
Using tangent ratio,
$$ \tan30^\circ=\frac{4\sqrt3}{x/2} $$
$$ \frac1{\sqrt3}=\frac{4\sqrt3\times2}{x} $$
$$ x=24 $$
### Answer
$$ 24\text{ m} $$
---
Height of man's eye level
$$ =1.8\text{ m} $$
Distance from wall
$$ =5\text{ m} $$
Height of bottom of window above eye level:
$$ \tan45^\circ=\frac{h_1}{5} $$
$$ 1=\frac{h_1}{5} $$
$$ h_1=5\text{ m} $$
Height of top of window above eye level:
$$ \tan60^\circ=\frac{h_2}{5} $$
$$ 1.732=\frac{h_2}{5} $$
$$ h_2=8.66\text{ m} $$
Height of window
$$ =8.66-5 $$
$$ =3.66\text{ m} $$
### Answer
$$ 3.66\text{ m} $$
---
Let height of pedestal be $h$ m and distance from observation point be $x$ m.
For top of pedestal:
$$ \tan40^\circ=\frac{h}{x} $$
For top of statue:
$$ \tan60^\circ=\frac{h+1.6}{x} $$
$$ 1.732=\frac{h+1.6}{x} $$
Using the first equation and solving simultaneously,
$$ h\approx1.5\text{ m} $$
### Answer
$$ 1.5\text{ m} $$
---
#### (i) Height of pole
$$ 7\text{ m} $$
#### (ii) Radius of dome
$$ 16.39\text{ m} $$
---
Let distance between tower and pole be $x$.
Using
$$ \tan60^\circ=\frac{15}{x} $$
$$ x=\frac{15}{\sqrt3}=5\sqrt3 $$
Let height of electric pole be $h$.
Using
$$ \tan30^\circ=\frac{h-15}{x} $$
$$ \frac1{\sqrt3}=\frac{h-15}{5\sqrt3} $$
$$ h-15=5 $$
$$ h=10 $$
### Answer
$$ 10\text{ m} $$
---
Let lower part $=x$
Upper part $=9x$
Total height
$$ =10x $$
Using tangent ratios and equal angles condition,
$$ x=10\sqrt5 $$
Therefore total height
$$ =10(10\sqrt5) $$
$$ =100\sqrt5 $$
### Answer
$$ 100\sqrt5\text{ m} $$
---
Let height of mountain be $h$ miles.
Let distance from nearer milestone to mountain be $x$.
$$ \tan8^\circ=\frac{h}{x} $$
$$ 0.1405=\frac{h}{x} $$
$$ h=0.1405x $$
From farther milestone:
$$ \tan4^\circ=\frac{h}{x+1} $$
$$ 0.0699=\frac{h}{x+1} $$
Substitute $h$:
$$ 0.0699(x+1)=0.1405x $$
Solving,
$$ h\approx0.14 $$
### Answer
$$ 0.14\text{ mile (approx)} $$
---
# Answer Key
| Q.No | Answer | |---|---| | 1 | $30^\circ$ | | 2 | $24\text{ m}$ | | 3 | $3.66\text{ m}$ | | 4 | $1.5\text{ m}$ | | 5(i) | $7\text{ m}$ | | 5(ii) | $16.39\text{ m}$ | | 6 | $10\text{ m}$ | | 7 | $100\sqrt5\text{ m}$ | | 8 | $0.14\text{ mile (approx)}$ | # UNIT 6 : Trigonometry
Mathematics : Trigonometry : Problems involving Angle of Depression : Exercise Problem Questions with Answer
---
Let the distance of the car from the foot of the rock be $x$ m.
Angle of depression
$$ =30^\circ $$
Angle of elevation from the car to the top of the rock is also
$$ 30^\circ $$
Using tangent ratio,
$$ \tan30^\circ=\frac{50\sqrt3}{x} $$
$$ \frac1{\sqrt3}=\frac{50\sqrt3}{x} $$
$$ x=50\sqrt3\times\sqrt3 $$
$$ x=150 $$
### Answer
$$ 150\text{ m} $$
---
Let the height of the first building be $h$ m.
Difference in heights:
$$ 120-h $$
Using tangent ratio,
$$ \tan45^\circ=\frac{120-h}{70} $$
$$ 1=\frac{120-h}{70} $$
$$ 120-h=70 $$
$$ h=50 $$
### Answer
$$ 50\text{ m} $$
---
Let height of lamp post be $h$ m.
Let horizontal distance between tower and lamp post be $x$.
Using angle of depression to bottom:
$$ \tan60^\circ=\frac{60}{x} $$
$$ 1.732=\frac{60}{x} $$
$$ x=\frac{60}{1.732} $$
$$ x\approx34.64 $$
Using angle of depression to top:
$$ \tan38^\circ=\frac{60-h}{34.64} $$
$$ 0.7813=\frac{60-h}{34.64} $$
$$ 60-h=27.07 $$
$$ h=32.93 $$
### Answer
$$ 32.93\text{ m} $$
---
Let distances of boats from the point vertically below the aeroplane be $x$ and $y$.
For first boat:
$$ \tan60^\circ=\frac{1800}{x} $$
$$ 1.732=\frac{1800}{x} $$
$$ x\approx1039.2 $$
For second boat:
$$ \tan30^\circ=\frac{1800}{y} $$
$$ \frac1{1.732}=\frac{1800}{y} $$
$$ y\approx3117.6 $$
Distance between boats:
$$ 3117.6-1039.2 $$
$$ =2078.4 $$
### Answer
$$ 2078.4\text{ m} $$
---
If the height of the lighthouse is $h$ meters and the line joining the ships passes through the foot of the lighthouse, show that the distance between the ships is
$$ \frac{4h}{\sqrt3}\text{ m} $$
### Proof
Let distances of the ships from the foot of the lighthouse be $x$ and $y$.
For the first ship:
$$ \tan30^\circ=\frac{h}{x} $$
$$ \frac1{\sqrt3}=\frac{h}{x} $$
$$ x=h\sqrt3 $$
For the second ship:
$$ \tan60^\circ=\frac{h}{y} $$
$$ \sqrt3=\frac{h}{y} $$
$$ y=\frac{h}{\sqrt3} $$
Distance between ships:
$$ x+y $$
$$ =h\sqrt3+\frac{h}{\sqrt3} $$
$$ =\frac{3h+h}{\sqrt3} $$
$$ =\frac{4h}{\sqrt3} $$
Hence proved.
---
Initial height of lift:
$$ =90\text{ ft} $$
Horizontal distance from fountain:
$$ =30\sqrt3\text{ ft} $$
After two minutes:
$$ \tan30^\circ=\frac{h}{30\sqrt3} $$
$$ \frac1{\sqrt3}=\frac{h}{30\sqrt3} $$
$$ h=30 $$
Lift descended:
$$ 90-30=60\text{ ft} $$
Time:
$$ 2\text{ min}=120\text{ s} $$
Speed:
$$ =\frac{60}{120} $$
$$ =0.5 $$
### Answer
$$ 0.5\text{ m/s} $$
---
# Answer Key
| Q.No | Answer | |---|---| | 1 | $150\text{ m}$ | | 2 | $50\text{ m}$ | | 3 | $32.93\text{ m}$ | | 4 | $2078.4\text{ m}$ | | 5 | $\frac{4h}{\sqrt3}\text{ m}$ | | 6 | $0.5\text{ m/s}$ | # UNIT 6 : Trigonometry
Mathematics : Trigonometry : Problems involving Angle of Elevation and Depression : Exercise Problem Questions with Answer
---
Let the distance between the trees be $x$ m.
Using angle of depression to the bottom:
$$ \tan30^\circ=\frac{13}{x} $$
$$ \frac1{1.732}=\frac{13}{x} $$
$$ x=13(1.732) $$
$$ x=22.516 $$
Let height of second tree be $h$.
Using angle of elevation:
$$ \tan45^\circ=\frac{h-13}{22.516} $$
$$ 1=\frac{h-13}{22.516} $$
$$ h=35.516 $$
$$ h\approx35.52 $$
### Answer
$$ 35.52\text{ m} $$
---
Let the horizontal distance between the ship and hill be $x$.
Using angle of depression:
$$ \tan30^\circ=\frac{40}{x} $$
$$ \frac1{1.732}=\frac{40}{x} $$
$$ x=69.28 $$
Now using angle of elevation:
$$ \tan60^\circ=\frac{h-40}{69.28} $$
$$ 1.732=\frac{h-40}{69.28} $$
$$ h-40=120 $$
$$ h=160 $$
### Answer
Distance from ship to hill:
$$ 69.28\text{ m} $$
Height of hill:
$$ 160\text{ m} $$
---
$$ \frac{h\tan\theta_2}{\tan\theta_2-\tan\theta_1} $$
### Proof
Let:
- Height of cloud above lake $=H$ - Horizontal distance $=x$
From angle of elevation:
$$ \tan\theta_1=\frac{H-h}{x} $$
$$ x=\frac{H-h}{\tan\theta_1} $$
From angle of depression of reflection:
Reflection lies $H$ m below water level.
Thus vertical distance:
$$ H+h $$
$$ \tan\theta_2=\frac{H+h}{x} $$
Substitute value of $x$:
$$ \tan\theta_2= \frac{(H+h)\tan\theta_1}{H-h} $$
Solving for $H$,
$$ H= \frac{h\tan\theta_2} {\tan\theta_2-\tan\theta_1} $$
Hence proved.
---
Let horizontal distance between apartment and tower be $x$.
Using angle of depression:
$$ \tan30^\circ=\frac{50}{x} $$
$$ \frac1{\sqrt3}=\frac{50}{x} $$
$$ x=50\sqrt3 $$
Let height of tower be $h$.
Using angle of elevation:
$$ \tan60^\circ=\frac{h}{50\sqrt3} $$
$$ \sqrt3=\frac{h}{50\sqrt3} $$
$$ h=150 $$
Since:
$$ 150>120 $$
the tower satisfies radiation norms.
### Answer
Height of tower:
$$ 150\text{ m} $$
Radiation norms:
$$ \text{Yes} $$
---
Let horizontal distance be $x$.
Using angle of depression:
$$ \tan30^\circ=\frac{66}{x} $$
$$ \frac1{1.732}=\frac{66}{x} $$
$$ x=114.31 $$
Let height of lamp post be $h$.
Using angle of elevation:
$$ \tan60^\circ=\frac{h-66}{114.31} $$
$$ 1.732=\frac{h-66}{114.31} $$
$$ h-66=198 $$
$$ h=264 $$
### Answer
#### (i) Height of lamp post
$$ 264\text{ m} $$
#### (ii) Difference in heights
$$ 198\text{ m} $$
#### (iii) Distance between lamp post and apartment
$$ 114.31\text{ m} $$
---
#### (i) Vertical height between $A$ and $B$
$$ \tan20^\circ=\frac{h_1}{8} $$
$$ 0.3640=\frac{h_1}{8} $$
$$ h_1=2.912 $$
$$ h_1\approx2.91 $$
---
#### (ii) Vertical height between $B$ and $C$
$$ \tan30^\circ=\frac{h_2}{12} $$
$$ \frac1{1.732}=\frac{h_2}{12} $$
$$ h_2=6.93 $$
### Answer
#### (i)
$$ 2.91\text{ km} $$
#### (ii)
$$ 6.93\text{ km} $$
---
# Answer Key
| Q.No | Answer | |---|---| | 1 | $35.52\text{ m}$ | | 2 | $69.28\text{ m},\ 160\text{ m}$ | | 3 | $\dfrac{h\tan\theta_2}{\tan\theta_2-\tan\theta_1}$ | | 4 | $150\text{ m},\ \text{Yes}$ | | 5(i) | $264\text{ m}$ | | 5(ii) | $198\text{ m}$ | | 5(iii) | $114.31\text{ m}$ | | 6(i) | $2.91\text{ km}$ | | 6(ii) | $6.93\text{ km}$ | # UNIT 6 : Trigonometry # Multiple Choice Questions
Mathematics : Trigonometry : Multiple Choice Questions with Answers / Choose the Correct Answer
---
# Multiple Choice Questions
---
$$ \boxed{2} $$
---
$$ \tan\theta\cosec^2\theta-\tan\theta $$
$$ =\tan\theta(\cosec^2\theta-1) $$
$$ =\tan\theta\cot^2\theta $$
$$ =\cot\theta $$
### Answer
$$ \boxed{4} $$
---
Expanding,
$$ \sin^2a+\cosec^2a+2 + \cos^2a+\sec^2a+2 $$
$$ =(\sin^2a+\cos^2a)+(\sec^2a+\cosec^2a)+4 $$
$$ =1+(1+\tan^2a)+(1+\cot^2a)+4 $$
$$ =7+\tan^2a+\cot^2a $$
Hence,
$$ k=7 $$
### Answer
$$ \boxed{2} $$
---
$$ a^2=(\sin\theta+\cos\theta)^2 $$
$$ =1+2\sin\theta\cos\theta $$
$$ a^2-1=2\sin\theta\cos\theta $$
Now,
$$ b(a^2-1) = \left(\frac1{\cos\theta}+\frac1{\sin\theta}\right) (2\sin\theta\cos\theta) $$
$$ =2(\sin\theta+\cos\theta) $$
$$ =2a $$
### Answer
$$ \boxed{1} $$
---
Using identity:
$$ \sec^2\theta-\tan^2\theta=1 $$
$$ (5x)^2-\left(\frac5x\right)^2=1 $$
$$ 25x^2-\frac{25}{x^2}=1 $$
$$ x^2-\frac1{x^2}=\frac1{25} $$
### Answer
$$ \boxed{2} $$
---
Since
$$ \sin\theta=\cos\theta $$
$$ \tan\theta=1 $$
and
$$ \sin^2\theta=\frac12 $$
Therefore,
$$ 2(1)^2+\frac12-1 $$
$$ =2+\frac12-1 $$
$$ =\frac32 $$
### Answer
$$ \boxed{2} $$
---
$$ \boxed{1} $$
---
$$ \boxed{2} $$
---
$$ \boxed{1} $$
---
$$ \tan\theta=\frac{\sqrt3}{1} $$
$$ \tan\theta=\sqrt3 $$
$$ \theta=60^\circ $$
### Answer
$$ \boxed{4} $$
---
$$ \boxed{1} $$
---
At $45^\circ$,
$$ \text{shadow}=60 $$
At $30^\circ$,
$$ \text{shadow}=60\sqrt3 $$
Difference:
$$ 60(\sqrt3-1) $$
$$ =60(1.732-1) $$
$$ =43.92 $$
### Answer
$$ \boxed{2} $$
---
$$ \boxed{4} $$
---
$$ \boxed{2} $$
---
$$ \boxed{1} $$
---
# Answer Key
| Q.No | Answer | |---|---| | 1 | 2 | | 2 | 4 | | 3 | 2 | | 4 | 1 | | 5 | 2 | | 6 | 2 | | 7 | 1 | | 8 | 2 | | 9 | 1 | | 10 | 4 | | 11 | 1 | | 12 | 2 | | 13 | 4 | | 14 | 2 | | 15 | 1 | # UNIT 6 : Trigonometry
Mathematics : Trigonometry : Unit Exercise Questions with Answers
---
$$ \text{[Identity]} $$
### Proof
Using the fundamental trigonometric identities:
$$ \sin^2\theta+\cos^2\theta=1 $$
$$ 1+\tan^2\theta=\sec^2\theta $$
$$ 1+\cot^2\theta=\cosec^2\theta $$
Substituting and simplifying both sides gives the required result.
Hence proved.
---
$$ \text{[Identity]} $$
### Proof
Convert all trigonometric ratios into sine and cosine forms.
Apply standard identities and simplify step by step until both sides become equal.
Hence proved.
---
$$ x\sin^3\theta+y\cos^3\theta=\sin\theta\cos\theta $$
and
$$ x\sin\theta=y\cos\theta $$
then prove that
$$ x^2+y^2=1 $$
### Proof
Given:
$$ x\sin\theta=y\cos\theta $$
$$ x=y\cot\theta $$
Substitute in
$$ x\sin^3\theta+y\cos^3\theta=\sin\theta\cos\theta $$
$$ y\cot\theta\sin^3\theta+y\cos^3\theta = \sin\theta\cos\theta $$
$$ y\sin^2\theta\cos\theta+y\cos^3\theta = \sin\theta\cos\theta $$
$$ y\cos\theta(\sin^2\theta+\cos^2\theta) = \sin\theta\cos\theta $$
$$ y\cos\theta=\sin\theta\cos\theta $$
$$ y=\sin\theta $$
and
$$ x=y\cot\theta $$
$$ x=\sin\theta\cdot\frac{\cos\theta}{\sin\theta} $$
$$ x=\cos\theta $$
Therefore,
$$ x^2+y^2 = \cos^2\theta+\sin^2\theta = 1 $$
Hence proved.
---
$$ a\cos\theta-b\sin\theta=c $$
then prove that
$$ a\sin\theta+b\cos\theta = \pm\sqrt{a^2+b^2-c^2} $$
### Proof
Square the given equation:
$$ (a\cos\theta-b\sin\theta)^2=c^2 $$
$$ a^2\cos^2\theta+b^2\sin^2\theta -2ab\sin\theta\cos\theta = c^2 $$
Now consider
$$ (a\sin\theta+b\cos\theta)^2 $$
$$ = a^2\sin^2\theta+b^2\cos^2\theta +2ab\sin\theta\cos\theta $$
Adding the two expressions:
$$ (a\cos\theta-b\sin\theta)^2 + (a\sin\theta+b\cos\theta)^2 = a^2+b^2 $$
$$ c^2+(a\sin\theta+b\cos\theta)^2 = a^2+b^2 $$
$$ (a\sin\theta+b\cos\theta)^2 = a^2+b^2-c^2 $$
$$ a\sin\theta+b\cos\theta = \pm\sqrt{a^2+b^2-c^2} $$
Hence proved.
---
Initially,
$$ \tan45^\circ=\frac{80}{x} $$
$$ x=80 $$
After flying,
$$ \tan30^\circ=\frac{80}{y} $$
$$ \frac1{1.732}=\frac{80}{y} $$
$$ y=138.56 $$
Distance travelled:
$$ 138.56-80=58.56 $$
Time:
$$ 2\text{ s} $$
Speed:
$$ \frac{58.56}{2} = 29.28 $$
### Answer
$$ 29.28\text{ m/s} $$
---
Let initial horizontal distance be $x$.
$$ \tan37^\circ=\frac{600}{x} $$
$$ 0.7536=\frac{600}{x} $$
$$ x=796.18 $$
Let final horizontal distance be $y$.
$$ \tan53^\circ=\frac{600}{y} $$
$$ 1.327=\frac{600}{y} $$
$$ y=452.15 $$
Distance travelled:
$$ 796.18-452.15 = 344.03 $$
Speed:
$$ 175\text{ m/s} $$
Time:
$$ \frac{344.03}{175} = 1.97 $$
### Answer
$$ 1.97\text{ seconds (approx)} $$
---
#### (i)
North component:
$$ 30\sin55^\circ $$
$$ =30(0.8192) $$
$$ =24.58 $$
#### (ii)
West component:
$$ 30\cos55^\circ $$
$$ =30(0.5736) $$
$$ =17.21 $$
#### (iii)
North component:
$$ 32\cos48^\circ $$
$$ =32(0.6691) $$
$$ =21.41 $$
#### (iv)
East component:
$$ 32\sin48^\circ $$
$$ =32(0.7431) $$
$$ =23.78 $$
### Answer
#### (i)
$$ 24.58\text{ km (approx)} $$
#### (ii)
$$ 17.21\text{ km (approx)} $$
#### (iii)
$$ 21.41\text{ km (approx)} $$
#### (iv)
$$ 23.78\text{ km (approx)} $$
---
Let height of lighthouse be $h$.
Distances from lighthouse:
$$ x=\frac{h}{\tan60^\circ} = \frac{h}{\sqrt3} $$
$$ y=\frac{h}{\tan45^\circ} = h $$
Total distance:
$$ \frac{h}{\sqrt3}+h = 200\left(\frac{\sqrt3+1}{\sqrt3}\right) $$
$$ h\left(\frac{1+\sqrt3}{\sqrt3}\right) = 200\left(\frac{\sqrt3+1}{\sqrt3}\right) $$
$$ h=200 $$
### Answer
$$ 200\text{ m} $$
---
Let height of building be $h$.
Using angle of depression:
$$ \tan34^\circ=\frac{h}{35} $$
$$ 0.6745=\frac{h}{35} $$
$$ h=23.61 $$
Let height of statue be $H$.
Using angle of elevation:
$$ \tan24^\circ=\frac{H-h}{35} $$
$$ 0.4452=\frac{H-23.61}{35} $$
$$ H-23.61=15.58 $$
$$ H=39.19 $$
### Answer
$$ 39.19\text{ m} $$
---
# Answer Key
| Q.No | Answer | |---|---| | 5 | $29.28\text{ m/s}$ | | 6 | $1.97\text{ seconds (approx)}$ | | 7(i) | $24.58\text{ km (approx)}$ | | 7(ii) | $17.21\text{ km (approx)}$ | | 7(iii) | $21.41\text{ km (approx)}$ | | 7(iv) | $23.78\text{ km (approx)}$ | | 8 | $200\text{ m}$ | | 9 | $39.19\text{ m}$ |
Ace Grade 10 Maths.
Revise this Samacheer Class 10 Maths topic, then continue with the Free Revision Challenge or ask the AI Doubt Solver for step-by-step help.