Trigonometric Functions — Maths STD 12 Science — Question

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\therefore \quad \cos \theta=\cos \frac{2 \pi}{3}\left(\text { As cos } \frac{\pi}{3}=\frac{1}{2} \text { and } \cos (\pi-A)=-\cos A\right)

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The general solution of $\cos \theta=\cos \alpha$ is $\theta=2 n \pi \pm \alpha$, where $n \in Z$.

$\therefore \quad$ The general solution of $\cos \theta=\cos \frac{2 \pi}{3}$ is $\theta=2 n \pi \pm \frac{2 \pi}{3}$ where $n \in Z$.

$\therefore \quad$ The general solution of $\cos \theta=-\frac{1}{2}$ is $\theta=2 n \pi \pm \frac{2 \pi}{3}$, where $n \in Z$.