If x = r cos $\theta$, y = r sin $\theta$ then x2 + y2 is equal to ______.

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KollegeApply · Accepted Answer

If x = r cos $\theta$, y = r sin $\theta$, then x2 + y2 is equal to r2. Explanation: If x = r cos$\theta$ and y = r sin$\theta$, then: x2 = (r cos $\theta$)2 = r2 cos2 $\theta$ y2 = (r sin $\theta$)2 = r2 sin2 $\theta$ x2 + y2 = r2 cos2 $\theta$ + r2 sin2 $\theta$ x2 + y2 = r2 (cos2 $\theta$ + sin2 $\theta$) Since sin2 $\theta$ + cos2 $\theta$ = 1 x2 + y2 = r2 (1) x2 + y2 = r2

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