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## Vector Magnitude Equation

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### #1hellz  Members

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Posted 23 August 2004 - 12:33 AM

Hey guys, I'm reading through 3D Math Primer for Graphics and Game Development, and on page 50 (for those that have the book handy), it gives the equation for calculating the magnitude of a vector. It works great and I understand it properly, bar one thing. Here's the example from the book:
||v|| = sqrt(vx² + vy² + vz²) (for a 3D vector v)

Example:

|| [5, -4, 7] || = sqrt(5² + (-4²) + 7²)
= sqrt(25, 16, 49)
= sqrt(90)
= 3sqrt(10)
= 9.4868

I understand it up to the point of sqrt(90) (obviously this works and gives the same result), but how does the author get 3sqrt(10) from all of that? Thanks in advance, -hellz

### #2davepermen  Members

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Posted 23 August 2004 - 12:34 AM

sqrt(90) == sqrt(9*10) == sqrt(9) * sqrt(10) == 3 * sqrt(10)
If that's not the help you're after then you're going to have to explain the problem better than what you have. - joanusdmentia

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### #3hellz  Members

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Posted 23 August 2004 - 12:37 AM

Ahhh, that makes sense. Thanks very much, and do you get the award for the fastest reply, or what. [grin]

-hellz

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