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Mathematics 9 Online
OpenStudy (anonymous):

more identity troubles.......

OpenStudy (anonymous):

\[\frac{ \cot^2x }{ cscx+1 }=\frac{ 1-sinx }{ sinx }\]

OpenStudy (anonymous):

verify the identity

OpenStudy (phi):

did you change everything to sin and cos ?

OpenStudy (anonymous):

\[\frac{ \frac{ \cos }{ \sin }^{2} }{ \frac{ 1 }{ \sin }+1 }\]

OpenStudy (phi):

yes along as the top is cos^2/sin^2

OpenStudy (phi):

I would add the bottom to get (1+sin)/sin then invert and multiply

OpenStudy (phi):

and because you are looking for sin (on the right side) I would change cos^2 to 1-sin^2

OpenStudy (phi):

how far did you get ?

OpenStudy (anonymous):

\[\frac{ \frac{ 1-\sin^2 }{ \sin } }{ \frac{ 1+\sin }{ \sin } }\]

OpenStudy (anonymous):

is that correct

OpenStudy (phi):

almost. it should say \[ \frac{ \frac{ 1-\sin^2 }{ \sin^2 } }{ \frac{ 1+\sin }{ \sin } } \]

OpenStudy (phi):

now change the division by (1+sin)/sin to a multiply by sin/(1+sin)

OpenStudy (phi):

remember \[ \cot^2 = \frac{\cos^2}{\sin^2} \]

OpenStudy (anonymous):

OH! the top changes to cos^2/sin^2 because 1-sin^2=cos^2!

OpenStudy (phi):

we started with cot^2 change to cos^2/sin^2 and then to (1-sin^2)/sin^2 that is the top now multiply by the inverse of the bottom. multiply by sin/(1+sin)

OpenStudy (phi):

I would factor the 1-sin^2 (it's a difference of squares)

OpenStudy (anonymous):

Oh... so when you cancel out you get 1-sin^2/sin

OpenStudy (phi):

how about this: \[ \frac{ \frac{ 1-\sin^2 }{ \sin^2 } }{ \frac{ 1+\sin }{ \sin } } = \frac{ 1-\sin^2 }{ \sin^2 } \cdot \frac{ \sin }{ 1+\sin }\]

OpenStudy (anonymous):

or I mean 1-sin/sin

OpenStudy (phi):

you can factor 1-sin^2 to (1-sin)(1+sin)

OpenStudy (anonymous):

and then |dw:1360170953425:dw|

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