Question

the questions is
1 . given A= 60° and B= 30° prove that :
a) cos ( A+B ) = cos A cos B - sin A sin B
please answer the questions​

Answer 1

Step-by-step explanation:

youll just have to know that the value of cos60 is 1by2 and cos30 is root 3by2

and sin 60 is root 3by 2 and sin 30 is 1 by2