Q13 of 268 Page 4

Show by an example that
cos A – cos B ≠ cos (A – B)

Let A = 60^o and B = 30^o, then

L.H.S.

R. H. S.

L.H.S. R.H.S

If sin (A + B) = cos (A – B) = , fins A and B.

If sin (A – B) = 1/2, cos(A + B) = 1/2; 0^o<A+B<90^o; A > B, find A and B.

Show by an example that

cos C + cos D ≠ cos (C + D)

Show by an example that

sin A + sin B ≠ sin (A + B)

Show by an example thatcos A – cos B ≠ cos (A – B)