Please help, precalc test tomorrow! Question is find all solutions on interval 0 less than or equal to theta less than or equal to 2 pi for cos(2theta)+1=0 I'm confused on how to get 2theta.....

Question

Please help, precalc test tomorrow! Question is find all solutions on interval 0 less than or equal to theta less than or equal to 2 pi for cos(2theta)+1=0       I'm confused on how to get 2theta.....

mrnood · Answer

subtract 1 from each side first...

what is the new equation?

anonymous · Answer

$$\cos2\theta=-1$$

nay_af · Answer

Give me a minute. Let me solve it.

anonymous · Answer

thank you!

nay_af · Answer

Solved. Please wait till I attach the image file for its solution.

nay_af · Answer

Take a look. I hope I haven't made any mistake in it.

anonymous · Answer

Thank you so much! How'd you get pi/2, and 3pi/2 for theta?

nay_af · Answer

2 Theta = Pi, 3Pi, 5Pi, ....

Divide both the sides by 2,

Theta = Pi/2, 3Pi/2, 5Pi/2, ....

anonymous · Answer

Ohh okay! Thank you!

nay_af · Answer

You're welcome.

mrnood · Answer

@cenochs
so - could you do a similar question yourself now? did you learn and absorb the process in the complete answer that was given to you.

If the same question came up tomorrow do you understand HOW to do it?

anonymous · Answer

A similar question did come up, but we didn't get the tests back yet. I'm not sure if I got it right, but I got an A so I'm happy :)

nay_af · Answer

@cenochs: Congratulations on attaining A. I am proud of you.

anonymous · Answer

@Nay_Af I was pretty surprised. I guess studying paid off this time :) ! Thank you!