Question

PROVE cos60.cos30-sin60.sin30=cos 90

Answer 1

hello!

Here is the answer of your question in the picture above...

hope this helps uh...

:D

Answer 2

Answer:

Step-by-step explanation:  

cos 60° = √3/2, cos 30° = 1/2, sin 60° = 1/2, sin 30° = √3/2

Then, cos 60°.cos 30° - sin 60°. sin 30° = √3/2 . 1/2 - 1/2 . √3/2

⇒√3/4 - √3/4 = 0 = cos 90°   [∵ cos 90° = 0]