Question

Using the fact that sin (A+ B) = sinAcos B + cosAsin B and the differentiation,
obtain the sum formula for cosines.

Answer 1

@ajprincess @nitz

Answer 2

@LilySwan

Answer 3

derivate it wrt to A and u will get the answer

Answer 4

How ?

Answer 5

differentiating the above equation partially wrt to A,
cos(A+B)=(cos B)(cos A)-(sinA)(sin B)

Answer 6

DURING PARTIAL derivative of sin A cos(B) wrt to A ,cos(B) remains constant and derivative of sin(A) is cos(A)

Answer 7

ANYTHING WRONG?

Answer 8

http://www.intmath.com/analytic-trigonometry/6-express-sin-sum-angles.php

Answer 9

Thankyou Madam and Sir