Tuesday, May 20, 2014

How do you verify the identity `tanx csc^2x-tanx=cotx` ?

Hello!


Recall the definitions of tan, csc and cot:


`tan(x)=sin(x)/cos(x),`  `csc(x)=1/sin(x), cot(x)=cos(x)/sin(x).`



Therefore the left part is equal to


`sin(x)/cos(x) * 1/(sin^2(x))-sin(x)/cos(x) =sin(x)/cos(x) (1/(sin^2(x))-1)=`


`=sin(x)/cos(x) * (1-sin^2(x))/(sin^2(x)) =sin(x)/cos(x) * (cos^2(x))/(sin^2(x))=cos(x)/sin(x),`



which is really equal to the right part, Q.E.D.

Hello!


Recall the definitions of tan, csc and cot:


`tan(x)=sin(x)/cos(x),`  `csc(x)=1/sin(x), cot(x)=cos(x)/sin(x).`



Therefore the left part is equal to


`sin(x)/cos(x) * 1/(sin^2(x))-sin(x)/cos(x) =sin(x)/cos(x) (1/(sin^2(x))-1)=`


`=sin(x)/cos(x) * (1-sin^2(x))/(sin^2(x)) =sin(x)/cos(x) * (cos^2(x))/(sin^2(x))=cos(x)/sin(x),`



which is really equal to the right part, Q.E.D.

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