Solving Trig Equations

**adkinsjr** · September 4th 2009, 02:32 PM

Ok, I have to take an accuplacer, I was doing a practice test online to prepare. I was given the equation:

$\sin(2\theta)+3=4$

I need to find $\theta$

$\sin(2\theta)=1$

When the sine of an angle is equal to one on $[0,2\pi]$ then the angle must be equal to $\frac{\pi}{2}$ right? So I have:

$2\theta=\frac{\pi}{2}$

$\theta=\pi$

The practice test I as doing is mulitple choice. Of course $\pi$ was actually the wrong answer

. Where am I going wrong here?

**alexmahone** · September 4th 2009, 02:47 PM

Originally Posted by adkinsjr

Ok, I have to take an accuplacer, I was doing a practice test online to prepare. I was given the equation:

$\sin(2\theta)+3=4$

I need to find $\theta$

$\sin(2\theta)=1$

When the sine of an angle is equal to one on $[0,2\pi]$ then the angle must be equal to $\frac{\pi}{2}$ right? So I have:

$2\theta=\frac{\pi}{2}$

$\theta=\frac{\pi}{4}$

Fixed the last statement.

**pacman** · September 4th 2009, 06:12 PM

You screwed the last line of your solution,

it should be pi/4 not pi

**adkinsjr** · September 5th 2009, 06:34 PM

lol, ok

thanks.

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