vectors a and b have magnitudes 3 and 5. The angle between the vectors is 130 degrees. determine the magnitude of the vector -a x 4b (cross product) the answer is 46 but I don't know how to get to that answer

Question

amistre64 · Answer

let a = (3,0)
let b= (5cos(130),5sin(130))

amistre64 · Answer

might as well make them 3D, tack on a ,0 for the z component

amistre64 · Answer

take the determinant:


        x              y            z         x                y
       -3             0           0        -3               0
20cos(130)  20sin(130)  0  20cos(130)  20sin(130)

(0,0,-60sin(130))

the magnitude should be 60sin(130)

amistre64 · Answer

45.96

anonymous · Answer

thanks a lot!