[Toán 12] Tính tích phân

N

nguyenbahiep1

$\frac{sin2x}{\sqrt{2}.sin(x+\frac{\pi}{4})}$

đặt $x+ \frac{\pi}{4} = t$

$\frac{sin(2t-\frac{\pi}{2})}{sint} = \frac{-cos2t}{sint} = \frac{2sin^2t-1}{sint } \\ \\ = 2siint - \frac{1}{sint}$

Ta giải
$\frac{1}{sint} = \frac{sint}{sin^2t} = \frac{sint}{1-cos^2t}$

đặt $cost = u$ là xong
 
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