How do you integrate $int tanx$ using substitution?

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Answer 1 · 2016-07-19T11:34:28

$int tanx dx = -ln(cosx) + C$

$tanx = sinx/cosx$

$int sinx/cosx dx$

Let $u = cosx implies du = -sinxdx$

$therefore -int (du)/u = -ln(u) + C$

$therefore int tanx dx = -ln(cosx) + C$

How do you integrate int tanxint tanx using substitution?