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