To solve this integral, you have to use substitution.
Integral ( sin(x) / cos^2(x) ) dx
I'm going to change the form of this question to make something obvious when I do the substitution.
Integral ([1/cos^2(x)]) [sin(x)] dx
Now, we begin our substitution.
Let u = cos(x). Then
du = -sin(x) dx, and
-du = sin(x) dx
Note the sin(x)dx attached at the end of our integral; I grouped them together specifically to show how (-du) would replace it entirely, due to what we just solved for. Now, our integral becomes
Integral (1/[u]^2)(-du)
Let's pull out that minus sign, which means we're effectively pulling out -1. We can *always* pull out constants in integrals.
(-1) * Integral (1/u^2) du
Remember that 1/u^2 is the same as u^(-2). Therefore, our integral becomes:
(-1) * Integral (u^(-2)) du
and now we use our reverse power rule.
(-1) [u^(-1)]/(-1) + C
reducing it further,
-1/u + C
And then substitution u = cos(x) back, we get
-1/cos(x) + C
2006-12-11 04:40:49
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answer #1
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answered by Puggy 7
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1/cos(x)
this is an integral
so you can solve this integral by using a simpole substution
You let u = cos x
du = -sin x dx
your integral then becomes -1/u^2 = 1/u
change u and you get 1/cos(x)
2006-12-11 04:43:43
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answer #2
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answered by Ant C 1
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it fairly is a confusing one, and is superb left memorized. vital ( a million/sin(x) dx ) that's comparable to vital ( csc(x) dx ) to unravel this, we predict of of this as a fragment over a million. vital ( csc(x)/a million dx ) Multiply precise and backside via csc(x) - cot(x). vital ( csc(x) [ csc(x) - cot(x) ] / [csc(x) - cot(x)] dx ) strengthen the numerator. vital ( [ csc^2(x) - csc(x)cot(x) ] / [ csc(x) - cot(x)] dx ) to coach how the substitution will artwork, i will rearrange this expression. vital ( a million / [ csc(x) - cot(x)] [ csc^2(x) - csc(x)cot(x) ] dx ) that's the place we use substitution. permit u = csc(x) - cot(x). Then du = [ -csc(x)cot(x) - (-csc^2(x)) ] dx du = [ -csc(x)cot(x) + csc^2(x) ] dx du = [ csc^2(x) - csc(x)cot(x) ] dx using our substitution to that end, this will become vital ( (a million/u) du ) Which we are able to unravel, as ln|u| + C back-substituting u = csc(x) - cot(x), we get ln|csc(x) - cot(x)| + C
2016-12-11 06:57:11
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answer #3
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answered by goslin 4
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(sinx / (cos^2x)) = sinx /[(cosx)(cosx)=(tanx)(sec x)
hence Antiderivative(sinx / (cos^2x))
Antiderivative (tanx)(sec x)
= Secx + c
2006-12-11 04:50:57
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answer #4
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answered by Mathematishan 5
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