Vectors a and b have magnitudes 3 and 4 respectively Find th

Vectors a and b have magnitudes 3 and 4 respectively. Find their dot product if the sine of the angle between them is 4/5

Solution

a = 3
b = 4

sin = 4/5

cos = 3/5 or can be -3/5   as sin is positive , so angle can be between 0 and 180

dot product : a.b cos

: 12 cos : 12(±3/5)   : ± 36/5 answer !!!