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September 18, 2014

September 18, 2014

Posted by **Anonymous** on Thursday, April 26, 2012 at 4:55pm.

Please show step-by-step, thank you!

- Trig Question -
**Reiny**, Thursday, April 26, 2012 at 5:56pmconstruct a triangle in quad II with x=-4 and y = 3

since tanØ = y/x or opposite/adjacent

so r^2 = (-4)^2 + 3^2

r = 5

sinx = 3/5 and cosx = -4/5

you have to know that

sin 2x = 2sinxcosx = 2(3/5)(-4/5) = -24/25

cos 2x = cos^2 x - sin^2 x = 16/25 - 9/25 = 7/25

tan 2x = sin 2x/ cos 2x = (-24/25) / (7/25) = -24/7

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