How do you find the integral of (sinx)(5^x) dx(sinx)(5x)dx?

1 Answer
May 17, 2018

int 5^x sinx dx = (5^x(ln5sinx- cosx))/(1+ln^2 5)+C5xsinxdx=5x(ln5sinxcosx)1+ln25+C

Explanation:

Integrate by parts:

int 5^x sinx dx = int 5^x d/dx (-cosx) dx 5xsinxdx=5xddx(cosx)dx

int 5^x sinx dx = = -5^xcosx + int cosx d/dx(5^x) dx 5xsinxdx==5xcosx+cosxddx(5x)dx

int 5^x sinx dx = = -5^xcosx + ln5 int cosx 5^xdx 5xsinxdx==5xcosx+ln5cosx5xdx

and then again:

int 5^x sinx dx = = -5^xcosx + ln5 int d/dx(sinx) 5^xdx 5xsinxdx==5xcosx+ln5ddx(sinx)5xdx

int 5^x sinx dx = = -5^xcosx + ln5sinx5^x - ln5 int sinx d/dx( 5^x)dx 5xsinxdx==5xcosx+ln5sinx5xln5sinxddx(5x)dx

int 5^x sinx dx = = 5^x(ln5sinx- cosx) - ln^2 5 int sinx5^xdx 5xsinxdx==5x(ln5sinxcosx)ln25sinx5xdx

The integral now appears on both sides of the equation and we can solve for it:

(1+ln^2 5)int 5^x sinx dx = 5^x(ln5sinx- cosx)+C(1+ln25)5xsinxdx=5x(ln5sinxcosx)+C

int 5^x sinx dx = (5^x(ln5sinx- cosx))/(1+ln^2 5)+C5xsinxdx=5x(ln5sinxcosx)1+ln25+C