tana =¾ tanb = 1 nilai 5 cos(a+b)+cos (a-b) adalah

jawab

tan A = 3/4
sin A = 3/5
cos A = 4/5

tan B = 1
sin B = 1/2 √2
cos B = 1/2 √2


5 cos (A+B) + cos (A-B)
= 5 (cos A cos B - sin A sin B) + cos A cos B + sin A sin B)
= 4 ( cos A cos B - sin A sin B)
= 3 (4/5 . 1/2√2 - 3/5 . 1/2√2)
= 3 (1/2√2) (1/5)  ( 4 - 3)
= (3/10)√2