The angle of intersection between a curve and a plane

[usaplasticman]

Homework Statement

r(t)=(t^2+t)i+(t^3-4)j+(3-t)k

r(t) hits the xy plane at the point (12,23,0). Find the angle on intersection of r(t) with the xy plane at that point.

Angle=

Homework Equations

cosθ=(AxB)/lAllBl

The Attempt at a Solution

I find the answer was 0.0017 degree, but the answer was absolutely wrong...

please help me :)

 

[HallsofIvy]

You haven't actually shown what you did. What did you use for A and B?