# Pre-Cal (verifying trig identities)

posted by .

How would you verify the identity?

• Pre-Cal (verifying trig identities) -

• Pre-Cal (verifying trig identities) -

• thinking needed -

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.

• Pre-Cal (verifying trig identities) -

(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.

• Pre-Cal (verifying trig identities) -

Thanks, Reiny.

• Pre-Cal (verifying trig identities) -

I think I have the same book as you Crystal... I have no clue how to solve this thing... :p

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