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# Important trigonometry questions for class 11 Maths

Here are some good Important trigonometry questions for class 11 Maths

1.if $tan \theta = \frac {a}{b}$ , show that $\frac {a sin \theta – b cos \theta}{a sin \theta + b cos \theta}= \frac {a^2 – b^2}{a^2 + b^2}$

2.Prove that $sec^4 x – sec^x = tan^4x + tan^2 x$

3.Prove that $cosec x ( sec x -1) – cot x(1- cos x) = tan x – sin x$

4.if $2C = A + B$, prove that

$cot B = \frac {sin A – sin C}{Cos C – CosA}$

5. Find the values of the below expression

a. $cos 20^{\circ} cos 40^{\circ} cos 60^{\circ} cos 80^{\circ}$

b. $sin 10^{\circ} sin30^{\circ} sin 50^{\circ} sin70^{\circ}$

6.if $Sinx = \frac {3}{5} ,cos y=\frac {9}{41} , 0<x,y < \frac {\pi}{2}$, then find the values

a. sin (x -y)

b. tan (x-y)

c. cot (x+y)

7. Derive the values of the angle

a. $sin 18^{\circ}$

b. $tan15^{\circ}$

c. $sin 67 \frac {1}{2}^{\circ}$

8. Prove that

$cos 55^{\circ} + cos 65^{\circ} + cos175^{\circ}=0$

9.  If $y = cos^2x + sin^4x$ for all values of x, then prove that

$\frac {3}{4} \leq y \leq 1$

10. Find the solution of the trigonometric equation   $2 tan^2 x + sec^2 x = 2$  in the range $[0,2\pi]$

11. Which of the following is not correct?
(A) sin A = –1/5
(B) cos A = 1
(C) sec A =1/2
(D) tan A = 20

12.Show that $2 sin^2 y + 4 cos (x + y) sin x sin y + cos 2 (x + y) = cos 2x$

5

a. 1/16

b. 1/16

6.

a. -133/205

b. -133/156

c. -84/187

7.

a. $\frac {\sqrt {5} -1}{4}$

b. $2- \sqrt {3}$

c.$\frac {\sqrt {2+ \sqrt {2}}}{2}$

10.$( \pi/6, 5\pi/6, 7 \pi/6 ,11 \pi/6)$

11.c