First slide

Compound angles

Question

$\frac{4 \sin 7^{o} \sin 67^{o} \sin 53^{o}}{\sin 21^{o}} =$

Easy

A

1
B

2
C

3
D

4

Solution

$\begin{array}{l} W e h a v e \sin θ \cdot \sin (60 ° + θ) \sin (60 ° - θ) = \frac{1}{4} \sin 3 θ \\ ∴ \sin 7 ° \sin 67 ° \sin 53 ° = \frac{1}{4} \sin 21 ° \\ \Rightarrow \frac{4 \sin 7 ° \sin 67 ° \sin 53 °}{\sin 21 °} = 1 \end{array}$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App