Question

1.
In a Quadrilateral ABCD,
cos A.cos B + sin C sin D =
1) cos C cos D+ sin Asin B
2) cos C cos D-sin Asin B
3) sin C sin D-cos Acos B
4) sin A+sin B +sin C +sin D
(cosa -cos 3a) (sin 8a+sin 2)​

Answer 1

Answer:

Option 1) is correct

Step-by-step explanation:

A+C=B+D=180

COS(A+B)=COS (B+D)

COS A COS C- SIN A SIN C=COS B, COS D- SIN B SIN D

COS B COS D+SINA SIN C=COS A, COS C +SIN B SIN D

HOPE IT HELPS YOU TO