• Nov 12th 2007, 04:34 PM
mayflower29
We're learning how to solve quadratic trigonometric equations:

ex. 3sin^2x - 8sinx -3 = 0
(3sinx+1)(sinx-3) = 0
then go on from there...

but how do I solve this one?

cotxcosx=cosx ?

Do I sub in 1/tanx for cot x ? where do I go from there?

Id appreciate some help :)
• Nov 12th 2007, 07:17 PM
topsquark
Quote:

Originally Posted by mayflower29
We're learning how to solve quadratic trigonometric equations:

ex. 3sin^2x - 8sinx -3 = 0
(3sinx+1)(sinx-3) = 0
then go on from there...

but how do I solve this one?

cotxcosx=cosx ?

Do I sub in 1/tanx for cot x ? where do I go from there?

Id appreciate some help :)

I typically get them into a form where there are only sines and cosines, but for this one:
\$\displaystyle cot(x)cos(x) = cos(x)\$

\$\displaystyle cot(x)cos(x) - cos(x) = 0\$

\$\displaystyle (cot(x) - 1)cos(x) = 0\$

Means that
\$\displaystyle cot(x) - 1 = 0\$
or
\$\displaystyle cos(x) = 0\$

-Dan
• Nov 12th 2007, 07:29 PM
mayflower29
Thanks a lot! :D