Question

Find sin 22 cos 78 +sin 78 cos 22

Answer 1

sin (90-22)×cos 78+sin78+cos (90-22)

cos22×cos78+sin78+sin22

cos^2 90+sin^2 90

(1)^2 + (0)^2

1+0

1

Answer 2

sin 22° cos 78° + sin 78° cos 22° = 1

Given :

The expression sin 22° cos 78° + sin 78° cos 22°

To find :

Find the value of the expression

Formula :

sin (A + B) = sin A cos B + cos A sin B

Solution :

Step 1 of 2 :

Write down the given expression

The given expression is

sin 22° cos 78° + sin 78° cos 22°

Step 2 of 2 :

Find the value of the expression

We are aware of the Trigonometric formula that

sin (A + B) = sin A cos B + cos A sin B

Thus we get

sin 22° cos 78° + sin 78° cos 22°

= sin 22° cos 78° + cos 22° sin 78°

= sin (22° + 78°)

= sin 90°

= 1

Correct question : Find sin 22° cos 78° + sin 78° cos 22°

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