Saturday, June 4, 2011

Prove that `2 + sec(x) cosec(x) = (sin x + cos x)^2 / (sin x cos x).`

`2+secxcscx=(sinx+cosx)^2/(sinxcosx)`


To prove, consider the left side of the equation.


`2+secxcscx`


Express the secant and cosecant in terms of cosine and sine, respectively.


`=2+1/cosx*1/sinx`


`=2+1/(sinxcosx)`


To add, express them as two fractions with same denominators.


`=2*(sinxcosx)/(sinxcosx)+1/(sinxcosx)`


`=(2sinxcosx)/(sinxcosx) + 1/(sinxcosx)`


`=(2sinxcosx + 1)/(sinxcosx)`


Apply the Pythagorean identity `sin^2x+cos^2x=1` .


`=(2sinxcosx+sin^2+cos^2x)/(sinxcosx)`


`=(sin^2x+2sinxcosx+cos^2x)/(sinxcosx)`


And, factor the numerator.


`= ((sinx +cosx)(sinx+cosx))/(sinxcosx)`


`=(sinx+cosx)^2/(sinxcosx)`


Notice that this is the same expression that the right side of the equation have. Thus, this proves that the  `2+secxcscx=(sinx+cosx)^2/(sinxcosx)`  is an identity.

No comments:

Post a Comment

find square roots of -1+2i

We have to find the square root of `-1+2i` i.e. `\sqrt{-1+2i}` We will find the square roots of the complex number of the form x+yi , where ...