1) integrate sin3x cos7x

i assumed u=3x and another time u=7x

then i came up with the ans:

-1/3 cos3x * 1/7 sin7x

2) integrate sqrrt (1-4x^2) dx

using the integration substitution to get the form of sqrt(a^2-x^2)

let a^2 = 1/4 x=1/2sinx

sqrt(1/4-1/4sin^2x)

but then i couldnt continue...