# Simplifying math identity

• April 25th 2010, 04:40 PM
something3k
Simplifying math identity
this problem has been bugging me for a long time

1/1-secx + 1/1+secx

i keep ending up with 2/1-sec^2(x)

but the answer is -2cot^2(x)

can anybody help :( what am i doing wrong
• April 25th 2010, 05:17 PM
Gusbob
Quote:

Originally Posted by something3k
this problem has been bugging me for a long time

1/1-secx + 1/1+secx

i keep ending up with 2/1-sec^2(x)

but the answer is -2cot^2(x)

can anybody help :http://mathhelpforum.com/trigonometry/141395-simplifying-math-identity.html#post501341\" rel=\"nofollow\">
this problem has been bugging me for a long time

1/1-secx + 1/1+secx

i keep ending up with 2/1-sec^2(x)

but the answer is -2cot^2(x)

can anybody help :( what am i doing wrong

so, you have $\frac{2}{1-sec^{2}x}$

$sex^2x-tan^2x=1$

so,

$tan^2x = sec^2x -1$

$-tan^2x = -sec^2x+1 =1-sec^2x$

so your denominator is equivalent to $-tan^2x$, thus giving you

$\frac{2}{-tan^2x} = -2cot^2x$ [because $cotx = \frac{1}{tanx}$]