# AP Calculus Verifying a Solution to a Differential Equation Trig Function (question)

• Dec 25th 2012, 02:08 PM
asilvester635
AP Calculus Verifying a Solution to a Differential Equation Trig Function (question)
why did the -sin^2(x) change into -1 + cos^2x?
• Dec 25th 2012, 02:13 PM
BobP
Re: AP Calculus Verifying a Solution to a Differential Equation Trig Function (questi
$\displaystyle \sin^{2}x+\cos^{2}x = 1.$
• Dec 25th 2012, 02:23 PM
asilvester635
Re: AP Calculus Verifying a Solution to a Differential Equation Trig Function (questi
i don't get it
• Dec 25th 2012, 02:41 PM
Plato
Re: AP Calculus Verifying a Solution to a Differential Equation Trig Function (questi
Quote:

Originally Posted by asilvester635
i don't get it

Do you get that if $\displaystyle s^2+c^2=1$ then $\displaystyle -s^2=-1+c^2~?$
• Dec 25th 2012, 02:43 PM
BobP
Re: AP Calculus Verifying a Solution to a Differential Equation Trig Function (questi
It's a basic trig identity that by now, (judging by what you are doing), you should be familiar with.

It can be rewritten as

$\displaystyle -\sin^{2}x = -1 +\cos^{2}x.$
• Dec 25th 2012, 02:50 PM
asilvester635
Re: AP Calculus Verifying a Solution to a Differential Equation Trig Function (questi
yah i forgot its a trig identity.. thanks anyways