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Mathematics 17 Online
OpenStudy (anonymous):

precalc question

OpenStudy (anonymous):

\[\frac{ \sec \Theta }{ 1-\sin \Theta }= \frac{ 1+\sin \Theta }{ \cos^{3} \Theta }\]

OpenStudy (anonymous):

we cannot manipulate the properties of the trig identities so does anyone know how to solve it

OpenStudy (anonymous):

Do you want to solve or prove an identity?

OpenStudy (anonymous):

prove an identity

OpenStudy (anonymous):

cos^2x =1-sin^2 x =(1-sin x)(1+sinx)

OpenStudy (anonymous):

but we cannot manipualte identities like i tried multiplying by the conjugate on the left side which gave 1-sin^2theta but we cannot use that to say it equals cos^2 theta

OpenStudy (anonymous):

Sec theta = 1/cos theta substitute that for sec theta, and simplify.

OpenStudy (anonymous):

yeah our teacher said we cannot manipulate the identity like that

OpenStudy (anonymous):

That's not true; you probably misunderstood what your teacher said. sec theta = 1/cos theta, is a reciprocal function property, which is permissable to substitute when proving an identity.

OpenStudy (anonymous):

like we have to leave it as sin^2+cos^2=1

OpenStudy (anonymous):

he said making it 1-sin^2=cos^2 requires a whole separate proof which we are not allowed to do

OpenStudy (anonymous):

There is no way to prove that identity if you do not substitute 1/cos theta for sec theta.

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