Question

cos40°_ cos 50° = √2 Sin 5°

Answer 1

use cosC- cosD=2sinC+D/2sinD-C/2

Answer 2

Concept

Recall the formula we will use to solve the

cosC- cosD=2sin(C+D)/2sin(D-C)/2

Given

The equation cos40°- cos 50° = √2 Sin 5°.

To find

We have to verify this equation.

Solution

First consider left-hand side

cos40°- cos 50= 2sin(40+50)/2sin(50-40)/2

                        $=2\times \frac{1}{\sqrt{2} } \sin 5^{\circ}$

                        = √2 Sin 5°

                       = RHS

Hence equation verifyed.