# Math problem!

Discussion in 'General Off-Topic Chat' started by MaHe, May 30, 2009.

# Math problem!

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1. ### MaHeone lazy schmo

Member
Aug 4, 2006
Maribor
Need some quick trigonometry help here! 2 * cos 10 / sin 20 equals to 1 / sin 10; But how do you derive one from the another? Thanks!

Member
Jun 3, 2007
UK blud dun kno
Rearrange to get 1 on it's own and use 1-sin^2 = cos^2, then you have a quadratic equation

3. ### FAST6191Techromancer

Reporter
Nov 21, 2005
I will try my usual rule of not giving a direct answer but this case might be hard.

I assume degrees rather than radians (not that it matters at this stage but I have seen such things end up in calculus territory).

First stage: rearrange. I went for nothing as a denominator.

Second stage: trigonometric identities. Rather sly use of one of the more rare identities today, the ones you want are sum formulas for sine and cosine .
The one in question:
sin (s + t) = sin s cos t + cos s sin t

angle is 20 and nicely enough 10 + 10 equals 20 and 10 is the angle of choice in the other factors.

Hopefully you can see where things go from here.