Question

вычислить интеграл:
1) cos^3(x)*sin^2(x) dx
2)dx\(x^2+10x-1)

Answer 1

$1)\; \int cos^3x\cdot sin^2x\, dx=\int sin^2x\cdot cos^2x\cdot cosx\, dx=\\\\=\int sin^2x(1-sin^2x)cosx\, dx=[\, t=sinx,\; dt=cosx\, dx\, ]=\\\\=\int (t^2-t^4)dt=\frac{t^3}{3}-\frac{t^5}{5}+C=\frac{1}{3}sin^3x-\frac{1}{5}sin^5x+C$

$2)\; \; \int \frac{dx}{x^2+10x-1}=\int \frac{dx}{(x+5)^2-26}=[\, t=x+5,\; dt=dx\, ]=\\\\=\int \frac{dt}{t^2-26}=\frac{1}{2\sqrt{26}}\cdot ln\left |\frac{t-\sqrt{26}}{t+\sqrt{26}}\right |+C=\frac{1}{2\sqrt{26}}\cdot ln\left |\frac{x+5\sqrt{26}}{x+5+\sqrt{26}}\right |+C$