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Please help me with the integral (1 / (cosxcotx))?
I just cant figure out what way to go about it?
INT (1 / (cosxcotx))
I'm figuring it should come out to something like (secx) but cant find the means thereto. Thanks!
3 Answers
- 1 decade agoFavorite Answer
this is an identity you'll get to memorize!! but here's one way to figure it out
1/cosx = secx and 1/cotx =tanx
so the integral sec(x)tan(x) dx can be found using u substitution
u=sec(x)
du i.e the derivative of sec(x) = tan(x)sec(x) dx
integral 1 du = u + constant
u = sec(x)
so the answer is
sec(x) + constant!!
kind of a silly answer huh! gotta love trig identities!
- ?Lv 71 decade ago
cotx= cosx /sinx
1/ (cosx cotx)= sin x/cos^2x
INT (1/ (cosx cotx) dx = INT (sinx/cos^2x) dx
u=cosx , du =-sin x dx
= - INT (1/u^2) du = (1/u ) = 1/cosx = sec x + C
- 1 decade ago
cot x = cos x / sin x
cos x cot x = cos² x / sin x
INT ( 1/(cos x cot x))dx = INT (sin x / cos² x) dx
sin x dx = d (- cos x)
INT ( 1/(cos x cot x))dx = INT d(- cos x) / cos² x = - INT dy / y² = 1/y + C = 1/cos x + C = sec x + C
(temporary y = cos x)