[RESOLVED] Angle between two vectors.

[NoteMe]

I don't have any of my math books here, but I am reading in a game programming book about vectors, but I can't get the same result as the authour. I am getting something else all the time.

I'll give a rep to the first guy that gets the same result as me or the authour for these vectors:

v1 = [1.5, 3.0, 4.0]
v2 = [4.0, 1.0, 2.0]


PS: Please give the angle in both Rad and Deg.

Thanks
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[zaza]

Hi,

Two words for you, Product and Dot. Not necessarily in that order.

A dot B = mod(A)mod(B)cos(theta)

A.B = (1.5*4)+(3*1)+(4*2) = 6+3+8 = 17

mod(A) = sqrt((1.5^2)+(3^2)+(4^2)) = sqrt(2.25+9+16) = 5.22015....

mod(B) = sqrt((4^2)+(1^2)+(2^2)) = sqrt(16+1+4) = 4.58258...

Hence cos(theta) = 17 / sqrt(27.25*21) = 0.71065...

Hence theta = 44.7 degrees or 0.78 rad

What do you get?

zaza

PS. Lazy whatnot.

Please give the angle in both Rad and Deg.

[NoteMe]

Me:

Angle (Rad): 0.7803741
Angle (Deg): 44.7121424

Authour:

Angle (Rad): 0.26
Angle (Deg): 15.0




So I guess my Vertex class is working after all then.....Thanks for the help. I was going nuts..


- ØØ -