What is the integral of sin(101x)sin99(x)dx?

1 Answer
Jan 11, 2018

sin(101x)(sinx)99dx=1100sin(100x)(sinx)100+C

Explanation:

sin(101x)(sinx)99dx

=sin(100x+x)(sinx)99dx

=(sin(100x)cosx+cos(100x)sinx)(sinx)99dx

=sin(100x)(sinx)99cosxdx+cos(100x)(sinx)100dx

=1100sin(100x)(sinx)100-cos(100x)(sinx)100dx+cos(100x)(sinx)100dx

=1100sin(100x)(sinx)100+C