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The problem concern the position vectors r1=2.43mi-4.74mj and r2=-3.02mi+0.85mj.
Find the angle between the two vectors. Hint: Find the angle each makes with the +x-axis.

  • physics - ,

    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?
    = 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*3.02-4.74*.85=DDDDD
    so tan theta = CCCCC/DDDDDD

  • physics - ,

    I see I missed a sign on R2, correct that please.

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