Question

find the value of cos75 ×cos15_sin75×sin15​

Answer 1

Question :

Find the value of cos75°× cos15° - sin75° × sin15°.

Procedure :

• First of all we need to simplify the given expression
• Then we will perform the subtraction

Identity used :

• sin(90-x) = cos x
• cos(90-x) = sin x

Solution :

Part 1) Simplification :

➝ cos75°×cos15° - sin75° × sin15°

➝ cos75°× cos(90-75)° - sin75°× sin(90-75)°

➝ cos75° × sin75° - sin75°×cos75°

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Part 2) Subtraction

➝ cos75° × sin75° - sin75°×cos75°

➝ 0

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ANSWER :

cos75°×cos15° - sin75° × sin15° = 0