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Help this is for calc

Help this is for calc-example-1

2 Answers

4 votes

Answer:

theta=pi/4, 3pi/4, 5pi/4, 7pi/4

Explanation:

User Mhhorizon
by
4.9k points
4 votes

You can solve for
\sin^2\theta, then take square roots:


2\sin^2\theta=1\implies\sin^2\theta=\frac12\implies\sin\theta=\pm\frac1{\sqrt2}

Then


\theta=\frac\pi4+2n\pi,\frac{3\pi}4+2n\pi,-\frac\pi4+2n\pi,\text{ or }-\frac{3\pi}4+2n\pi

where
n is any integer; we get the following solutions in the interval
0\le\theta\le2\pi:


\boxed{\theta=\frac\pi4,\frac{3\pi}4,\frac{5\pi}4,\frac{7\pi}4}

Or, you can use the double angle identity:


\sin^2\theta=\frac{1-\cos(2\theta)}2=\frac12\implies1-\cos(2\theta)=1\implies\cos(2\theta)=0

Then


2\theta=\frac\pi2+n\pi\implies\theta=\frac\pi4+\frac{n\pi}2

where
n is any integer, and we get the same solutions as above within the prescribed interval.

User Stirfries
by
6.1k points