Question

Help me to solve this question​

Answer 1

`\left \{ {{\theta_1=(\pi )/(4) } \atop {\theta_2=(3\pi )/(4) }} \right. .`

Explanation:

`2*cos^2\theta-1=0\ \ \ \ (0^0\leq \theta\leq 360^0)\ \ \ \ \ \theta=?\\2*cos^2\theta-(sin^2\theta+cos^2\theta)=0\\2*cos^2\theta-sin^2\theta-cos^2\theta=0\\cos^2\theta-sin^2\theta=0\\cos2\theta=0\\0^0\leq \theta\leq 360^0\ \ \ \ \Rightarrow\\\left \{ {2\theta=(\pi )/(2)\ \atop 2\theta=(3\pi )/(2)\ } \right. \ \ \ \ \left \{ {{\theta_1=(\pi )/(4) } \atop {\theta_2=(3\pi )/(4) }} \right. .`

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