(adsbygoogle = window.adsbygoogle || []).push({}); 1. Three points P, Q and R have position vectors p, q and r respectively, where:

p=8i+11j, q=7i-5j and r=2i+4j.

Write down the vectors QP and QR and show that they are not perpendicular. Hence determine the angle PQR.

2. |QP|.|QR|cos(theta)

3. QP= QO+OP=i+16j

QR=QO+OR=-5i+9j

|QP|=root257

|QR|=root106

If the vectors are not perpendicular then a.b=0

a.b= QP=i+16j x QR=-5i+9j = (1)(-5)+(16)(9)=-5+144=139 - not perpendicular

a.b=|QP|.|QR|cos(theta)

cos(theta)=a.b/|QP|.|QR|=139/root257 x root106 = 32.6

Could anybody check to see how pathetic this attempt is, please?

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# Homework Help: Vector angle

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