$$26\cdot\int \sin^{2}x\sin\ 3xdx$$
$\frac{26\left(12\left(\cos(x)\right)^{5}-25\left(\cos(x)\right)^{3}+15\cos(x)+15С\right)}{15}$
$26\sin(x)\left(-4\left(\cos(x)\right)^{4}+5\left(\cos(x)\right)^{2}-1\right)$
