Posted by anonymous on Sunday, May 2, 2010 at 5:20pm.
I need help solving this problem algebraically, but I need to learn step by step!!
Thanks so much
cos 2x=cos x
How do I do it?
- MATH ANALYSIS - Reiny, Sunday, May 2, 2010 at 5:42pm
you should know that
cos 2x = 2cos^2 x - 1
so we have
2cos^2 x - 1 = cosx
2cos^2 x - cosx - 1 = 0
(2cosx + 1)(cosx -1) = 0
cosx = -1/2 or cosx = 1
x = 120° or 240° or x = 0 or 360
x = 0, 2π/3, 4π/3, 2π
- MATH ANALYSIS - anonymous, Sunday, May 2, 2010 at 5:54pm
Answer This Question
More Related Questions
- Trig - sum and difference formulas - Write the expression as a single ...
- Math - y=arccos(sin(x)), find dy/dx and sketch it's graph(I guess I can do this ...
- Algebra 1 - -3x + 6 < 21 I need help in solving this problem step by step. ...
- Calculus - Evaluate cos[2arctan(2)] Need step by step for this one. Thanks
- Algebra II - Solving the formula for the indicated variable. I=prt,for r I need ...
- algebra - Solving Systems by Substitution: 2. x=1-4y 2x+7y=3 I need help ...
- Algebra 2 - I need help trying to solve trigonometric identity problems I just ...
- Algebra - (5x10^14)-1 I need help with this problem. If you can please show me ...
- math - Solving Equations with Fractions 3m/5 - 1/2 = 7/10 solve for M i need a ...
- Trigonometry - I need help proving the following identity: 4(sin^6(x)+cos^6(x...