Posted by emily on Tuesday, May 18, 2010 at 6:56am.
how to solve y= 3cos2x + 5
pls help me

math  drwls, Tuesday, May 18, 2010 at 8:21am
Is that really cos(2x) or do you mean cos^2 x?
I will assume that you really do mean cos(2x). In that case
cos(2x) = cos^2 x  sin^2 x
= 2 cos^2 x 1
y = 6 cos^2x 3 + 5 = 6 cos^2 x  2
cos^2 x = (y+2)/6
cos x = sqrt[(y+2)/6)]
You can use that to solve for x, if that is what the question is all about.
You cannot solve a single equation for both x and y.
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