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Please solve RD Sharma Class 12 Chapter 19 Definite Integrals Exercise 19.4 (b) Question 26 maths textbook solution.

Answers (1)

Answer:-  \frac{\pi }{4}-\frac{1}{2}

Hints:-  You must know the integral rules of trignometric  functions with its limits.

Given:-  \int_{-\pi / 4}^{\pi / 4} \sin ^{2} x \cdot d x

Solution : \int_{-\pi / 4}^{\pi / 4} \sin ^{2} x \cdot d x

            \begin{aligned} &=\int_{-\pi / 4}^{\pi / 4} \frac{1-\cos 2 x}{2} \cdot d x \\ &=\frac{1}{2} \int_{-\pi / 4}^{\pi / 4}(1-\cos 2 x) \cdot d x \\ &=\frac{1}{2}[x-\sin 2 x]_{-\pi / 4}^{\pi / 4} \end{aligned}

            \begin{aligned} &=\frac{1}{2}\left[\frac{\pi}{4}-\sin 2 \times \frac{\pi}{4}-\left(\frac{-\pi}{4}\right)+\sin \left(2 \times \frac{-\pi}{4}\right)\right] \\ &=\frac{1}{2}\left[\frac{\pi}{4}+\frac{\pi}{4}-1+0\right] \\ &=\frac{2 \pi}{2 \times 4}-\frac{1}{2} \\ &=\frac{\pi}{4}-\frac{1}{2} \end{aligned}  

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