Amaths_vector 2

(a)
OP=2i+3j,OQ=-6i+4j,PR:RQ=k:1
OR
=[(1*2+(-6)k)/(k+1),(1*3+4k)/(k+1)]
=[(2-6k)/(k+1),(3+4k)/(k+1)]
[(2-6k)/(k+1)]i+[(3+4k)/(k+1)]j
OP.OR
=[2(2-6k)/(k+1)]+[3(3+4k)/(k+1)]
=13/(k+1)
OQ.OR
=[(-6)(2-6k)/(k+1)]+[4(3+4k)/(k+1)]
=52k/(k+1)
In this case OP.OR/|OP||OR|=OQ.OR/|OQ||OR|
13/(k+1)SQRT(13)=52k/(k+1)SQRT(52)
26=52k
k=2

只係打錯少少姐: 26 = 52k
k = 1/2