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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Specialist Mathematics => Topic started by: poohead on April 11, 2010, 03:57:51 pm

Title: ESSENTIAL MATH help?
Post by: poohead on April 11, 2010, 03:57:51 pm: hey guys
need help with q23 & 24 of 2b in essentil math
Title: Re: ESSENTIAL MATH help?
Post by: superflya on April 11, 2010, 04:12:26 pm: q24)

$\frac{(a_{1})^{2}}{|a|^{2}}+\frac{(a_{2})^{2}}{|a|^{2}}+\frac{(a_{3})^{2}}{|a|^{2}}$

$\frac{(a_{1})^{2}+(a_{2})^{2}+(a_{3})^{2}}{|a|^{2}}$

$|a|^{2}=a\cdot a$

$\Rightarrow \frac{(a_{1})^{2}+(a_{2})^{2}+(a_{3})^{2}}{(a_{1})^{2}+(a_{2})^{2}+(a_{3})^{2}}=1$
Title: Re: ESSENTIAL MATH help?
Post by: brightsky on April 11, 2010, 04:13:34 pm: This should help:

http://en.wikipedia.org/wiki/Direction_cosine
Title: Re: ESSENTIAL MATH help?
Post by: poohead on April 11, 2010, 04:20:16 pm: i think im stupid
:S
i dont get superfly or wikipedia working out :S
Title: Re: ESSENTIAL MATH help?
Post by: superflya on April 11, 2010, 04:23:52 pm: $\cos \alpha =\frac{a_{1}}{|a|} \cos \beta =\frac{a_{2}}{|a|} \cos \gamma =\frac{a_{3}}{|a|}$

then square.