Question

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In triangle ABC, the value of cos ( A - B) - cos (C) =?

THANK YOU

Answer 1

In Triangle ABC,

A + B + C = 180°
So,
C = 180° - ( A + B)
So,
cos ( A-B) - cos ( 180° - ( A+B))
= cos (A-B) - ( - cos (A+B)) because cos ( 180°-©) = - cos ©

So,
= cos(A-B) + cos(A+B)
= 2 cos ( (A-B+A+B)/2) cos ((A-B-A-B)/2)
= 2 cos (A) cos (-B)
= 2 cos A cos B

Hope this helps you !

Answer 2

Answer:

Step-by-step explanation: