# Solve a system of equations involving trig functions

• Feb 11th 2014, 01:51 PM
petenice
Solve a system of equations involving trig functions
Im trying to solve these two equations by elimination. But im stuck at this point. This is for a Diff Equation class and i just cant recall some of the trig rules.

\$\displaystyle -4cos(2x)-2sin(2x)p(x)+cos(2x)q(x)=0\$
\$\displaystyle -4sin(2x)+2cos(2x)p(x)+sin(2x)q(x)=0\$

Any help is appreciated. Thanks
• Feb 11th 2014, 02:20 PM
Prove It
Re: Solve a system of equations involving trig functions
You don't need trig rules, you need ALGEBRA rules. Choose which function you want to solve for (either p or q), which means you need to eliminate the other function.

Say you want to eliminate p, you will need to multiply all the first equation by cos(2x) and all the second equation by sin(2x) so that p has the same coefficients in both equations, then add the equations.
• Feb 11th 2014, 03:53 PM
petenice
Re: Solve a system of equations involving trig functions
OK, i understand. Thank you again Prove It.