1.II.13F

Complex Analysis or Complex Methods | Part IB, 2007

By integrating round the contour CRC_{R}, which is the boundary of the domain

DR={z=reiθ:0<r<R,0<θ<π4}D_{R}=\left\{z=r e^{i \theta}: 0<r<R, \quad 0<\theta<\frac{\pi}{4}\right\}

evaluate each of the integrals

∫0∞sin⁡x2dx,∫0∞cos⁡x2dx\int_{0}^{\infty} \sin x^{2} d x, \quad \int_{0}^{\infty} \cos x^{2} d x

[You may use the relations ∫0∞e−r2dr=π2\int_{0}^{\infty} e^{-r^{2}} d r=\frac{\sqrt{\pi}}{2} and sin⁡t≥2πt\sin t \geq \frac{2}{\pi} t for 0≤t≤π2⋅]\left.0 \leq t \leq \frac{\pi}{2} \cdot\right]

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