Question

Prove that
$cos(a + b) = cos \: a \: cos \: b - sin \: a \: sin \: b$
​

Answer 1

Answer:

Cos 15 ° = Cos ( 45° - 30 ° )

Cos ( A- B ) = CosA CosB + SinA SinB.

Cos( 45° - 30° ) = Cos45. Cos30+ Sin45.Sin30

Step-by-step explanation:

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