Find all values of theta in the interval 0<theta<360 2 cos^2 theta - 1=0
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Originally Posted by blame_canada100 Find all values of theta in the interval 0<theta<360 2 cos^2 theta - 1=0 $\displaystyle 2\cos ^2 \theta -1 = 0 $ $\displaystyle \cos ^2 \theta = \frac{1}{2}$ $\displaystyle \cos \theta = \mp \frac{1}{\sqrt{2}}$ theta equal the angle 45 in all quarters
Hello blame_canada100 Originally Posted by blame_canada100 Find all values of theta in the interval 0<theta<360 2 cos^2 theta - 1=0 Alternatively, you could use $\displaystyle \cos2\theta = 2\cos^2\theta - 1$ So $\displaystyle \cos2\theta = 0$ $\displaystyle \Rightarrow 2\theta = 90^o,\,270^o,\,450^o,\,630^o$ Then divide by $\displaystyle 2$. Grandad
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