Question

Diketahui sin A= 3/5 dan sec B= 13/12, dengan A sudut lancip dan B dikuadran III. NIlai cos A cos B + sin A sin B=
A. -63/65
B. -33/65
C. 15/65
D. 33/65
E. 63/65

Answer 1

Sin A = 3/5
x= √5^2-3^2
x= √25-9 = √16 =4

cos A= 4/5

sec B = 13/12
cos B= 12/13
y= √169-144 = √25
y=5
SIN B = 5/13

cos A cos B + sin A sin B
=4/5(-12/13) + 3/5(-5/13)
=-48/65-15/65
=-63/65 (A)