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Math Vectors

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pastyear:
ya
P of AB =( 1  -1  0)
P of PA  =( 2t    -3-t    1+t)
P AB  dot P PA = 3t+3

Mod P AB = square root 2
Mod P PA = square root 6tsquare + 8t + 10

pastyear:
cos 60 = 1/2  = mod 3t+3 / square root of  6t square  + 8t + 10 times square root 2 Mod

Twinkle Charms:

--- Quote from: pastyear on May 22, 2010, 04:16:23 pm ---ya
P of AB =( 1  -1  0)
P of PA  =( 2t    -3-t    1+t)
P AB  dot P PA = 3t+3

Mod P AB = square root 2
Mod P PA = square root 6tsquare + 8t + 10

--- End quote ---
look thts where ur makin mistake , its not PA, its AP

pastyear:
still cannot get
i get 3t square + 8t  +2

Twinkle Charms:
AP=(-2t  3+t  -1-t) and AB=(1  -1  0)

did you get these vectors??

(-2t   3+t   -1-t).(1  -1  0)= |AP|.|AB| cos60

|AP| means modulus of AP = rootof [(-2t)^2  +  (3+t)^2  +  (-1-t)^2] and similarly for |AB|.

did you do it this way?

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