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If f(sin x) = cos 2x, find f(cos x).
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It is given that f(sin x) = cos 2x. We have to determine f(cos x)
cos x = sin (90 - x)
f(sin (90 - x)) = cos (2*(90 - x))
=> cos (180 - 2x)
=> -cos 2x
For the given function, f(cos x) = -cos 2x
Posted by justaguide on October 21, 2011 at 6:48 PM (Answer #1)
By the basic trigonometry we know that cosx=sin(90-x)
so put x=90-x in the function
f(sin x) = cos 2x
now cos(x)=-cos(pie -x)
so f(cos x)=-cos2x.
this problem is similar to Algebra equations after we have inserted the value of x as 90-x
Posted by kanishkporwal on October 21, 2011 at 9:35 PM (Answer #2)
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