Tuesday

October 21, 2014

October 21, 2014

Posted by **Abbey** on Thursday, March 11, 2010 at 1:49pm.

sin2x sinx = cosx

2cos(x) (1/2-sin^2x) = 0

Then I got 3pi/2, pi/2, pi/6 and 5pi/6

Then I substituted 0-3 and got 3pi/2 , 5pi/2 , 9pi/2 , pi/2, pi/6, 7pi/6, 13pi/6 , 19pi/6 , 5pi/6 , 11pi/6 , 17pi/6 and 23pi/6.

My teracher said that I had to fix my answer and that there could be nothing greater than 2pi. Which ones do I need to take out?

- Pre-Cal(Please check) -
**drwls**, Thursday, March 11, 2010 at 2:26pm2 sinx cosx sin x = 2 sin^2x cos x= cosx

2 (1-cos^2x) cosx = cos x

cosx - 2 cos^3 x = 0

cosx (1-2 cos^2x) = 0

cosx = 0 or sqrt(1/2)

x = pi/2, 3 pi/2, pi/4 or 3 pi/4

- Pre-Cal(correction) -
**drwls**, Thursday, March 11, 2010 at 2:28pmThe last root should be 7 pi/4, not 3 pi/4

**Answer this Question**

**Related Questions**

Pre-Cal(Please help) - Approximate the equation's soultions in the interval (o...

Pre-Cal - Approximate the equation's soultions in the interval (o, 2pi). If ...

maths - hey, i would really appreciate some help solving for x when: sin2x=cosx ...

check math - Here are my answers. Can you check if I got the right answers? ...

Pre-Cal(Please check) - 1) Find all the solutions of the equation in the ...

Pre-Cal(Please check) - 1) Find all the solutions of the equation in the ...

Math - Approximate the equation's solutions in the interval (0,2pi). sin2x sinx...

Trig....... - I need to prove that the following is true. Thanks (2tanx /1-tan^x...

Trig - Verify the identity: tanx(cos2x) = sin2x - tanx Left Side = (sinx/cosx)(...

Math - Can I please get some help on these questions: 1. How many solutions does...