Asked by Crystal

How would you verify the identity?
sin^1/2x-cosx-sin^5/2xcosx=cos^3xradsinx
Answered by bobpursley
what is rad?
Answered by Crystal
radical
Answered by bobpursley
multiply both sides by the sqrt sinx

sinx-cosxsinx-sin^3x cosx=cos^3x sinx
sinx-cosxsinx-(1-cos^2x)sinxcosx=
sinx(1-cosx)-sinxcosx+sinxcox^3x=
sinx(1-cosx-cosx)+sinx cox^3x=
Hmmm. This is telling me the identity does not exist, because sinx(1-2cosx) is not zero.

check my work. There has to be an error here, but I am certain this is (was ) leading somewhere.
Answered by Reiny
I read your identity as
(sinx)^(1/2) - cosx - (sinx)^(5/2)*cosx = (cosx)^3 *(sinx)^(1/2)

I picked 30 degrees, and the
left side was NOT equal to the right side.

So the way you typed it, it is not an identity.
Answered by bobpursley
Thanks, Reiny.
Answered by John
I think I have the same book as you Crystal... I have no clue how to solve this thing... :p
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