Question

Diketahui sudut antara vektor-vektor a = 2i - j +3k dan b =i+3j -pk adalah 1/3 pi, tentukan nilai p

Answer 1

A . b = besar a . besar b cos alfa
( 2 - 3 - 3p ) = (akar 14)   ( akar 10+p^2 ) . cos 60
( -1 -3p ) = (akar 14 ( 10 + p^2 )) . 1/2
-2 - 6p = akar ( 14 (10+p^2) )
(-2-6p)^2 = (14(10+p^2))
36p^2 + 24p + 4 = 140 + 14 p^2
22 p^2 + 24 p - 136 = 0
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