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Mathematics 21 Online
OpenStudy (anonymous):

Simplify the trigonometric expression.

OpenStudy (anonymous):

\[\frac{ \sin^2 \theta }{ 1- \cos \theta } \]

hartnn (hartnn):

multiply numerator and denominator by 1+ cos theta

hartnn (hartnn):

then you can use the relation, \((a+b)(a-b)=a^2-b^2\)

OpenStudy (anonymous):

That doesn't seem right

hartnn (hartnn):

what doesn't seem right ? "multiplying numerator and denominator by 1+ cos theta" ? have you tried it ?

OpenStudy (anonymous):

yes, i tried it.. the answer doesnt seem right

hartnn (hartnn):

there's an another way too, if this feels confusing... what answer u got ?

OpenStudy (anonymous):

i got sin theta

hartnn (hartnn):

naah...how ? the denominator : (1+ cos theta )(1- cos theta) = 1-cos^2 theta =...... ?

OpenStudy (anonymous):

I'm not good at math, none of this is making sense to me...

hartnn (hartnn):

none!? my heart just broke :P \(\large \frac{ \sin^2 \theta }{ 1- \cos \theta }=\frac{( \sin^2 \theta )(1+cos \theta)}{( 1- \cos \theta)(1+cos \theta) }=\frac{( \sin^2 \theta )(1+cos \theta)}{1-\cos^2 \theta }\) using \((a+b)(a-b)=a^2-b^2\)

hartnn (hartnn):

got that^ ?

OpenStudy (anonymous):

OKay yeah that makes some sense

hartnn (hartnn):

and what does 1- cos^2 theta equal to ?? (hint : \(\sin^2 x+\cos^2x=1\))

OpenStudy (anonymous):

Does'nt it = sin^2 theta?

OpenStudy (anonymous):

or am i totally just getting this wrong?

hartnn (hartnn):

it exactly = sin^2 theta! good :) so, what gets cancelled ? what remains ?

OpenStudy (anonymous):

the sin^2 theta's get cancelled?

OpenStudy (anonymous):

wait not the cos gets cancelled

hartnn (hartnn):

the sin^2 theta's get cancelled, what remains is 1+cos theta thats your answer.

OpenStudy (anonymous):

thanks :)

hartnn (hartnn):

welcome ^_^

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