Sin a = 3/5 Coa b = 7/25 a tumpul dan b lancip Maka cos (a-b) =

jawab

sin A = 3/5= y/r
x = √(r²-y²)
x = √(5²-3²)
x= 4
<A tumpul → cos A = - x/r = - 4/5

Cos B = 7/25 = x/r
y = √(r² -x²)
y = √(25²-7²)
y = 24
<B lancip,→ sin B = y/r = 24/25

cos (A -B) = cos A cos B + sin A sin B
= -4/5. 7/25 + 3/5 . 24/25
= - 28/125 + 72/25
= 44/25