How do I evaluate int(1-sinx)/cosx dx1sinxcosxdx?

1 Answer
Jan 31, 2015

=ln(1+sin(x))+c=ln(1+sin(x))+c

Well, this one is a little bit tricky...
I started with the idea that the result must be a logarithm...
So I did a little manipulation to get to a friendlier version of your function by multiplying and dividing by:

(1+sin(x))/(1+sin(x))1+sin(x)1+sin(x); so I get:

int(1-sin(x))/cos(x)*(1+sin(x))/(1+sin(x))dx=1sin(x)cos(x)1+sin(x)1+sin(x)dx=
=int(1-sin^2(x))/(cos(x)(1+sin(x)))dx==1sin2(x)cos(x)(1+sin(x))dx=
=int(cos^2(x))/(cos(x)(1+sin(x)))dx==cos2(x)cos(x)(1+sin(x))dx=
=int(cos(x))/((1+sin(x)))dx==cos(x)(1+sin(x))dx= which is a manipulated version of your original function and we can call it (1). The integral of (1) is indeed a logarithm:

=ln(1+sin(x))+c=ln(1+sin(x))+c

Which derived gives (1) or your original function!!!!!