physics
posted by Wykeena on .
The problem concern the position vectors r1=2.43mi4.74mj and r2=3.02mi+0.85mj.
Find the angle between the two vectors. Hint: Find the angle each makes with the +xaxis.

do the dot product, and the magnitude of the cross product.
cross product= r1XR2=magR1*magR2*sinTheta
dot product= magR1*magR2*cosTheta
cross product/dot product = tan theta
solve for theta.
How do you get cross product?
r1XR1=(2.3i4.74j)X(3.02i+.85j)
= 2.31iX(3.02i+.85j) + (4.74j)X(3.02i+.85j)
well iXi=0, iXj= k, jXi=k, jXj=0
or = 2.31*.85k+4.74*3.02k=CCCCc
How do you get the dot product?
r1.r2= 2.3*3.024.74*.85=DDDDD
so tan theta = CCCCC/DDDDDD 
I see I missed a sign on R2, correct that please.