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# C4 Integration help !!!! watch

1. I have tried this sum 3-4 times and its impossible!!! Someone help me asap !!

Use the substitution x=sec(theta) and integration to find the value of

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2. have u used the identity sec^2x =1 tan^2x
3. (Original post by whizz-kid)
have u used the identity sec^2x =1 tan^2x
U mean sec^2x= 1+tan^2x ? Why do you need that here? Cant you just integrate Sec^2x directly?
4. (Original post by warkan)
U mean sec^2x= 1+tan^2x ? Why do you need that here? Cant you just integrate Sec^2x directly?
No when you make the substitution x=sec u, then the x^2-1 becomes sec^2 u-1=tan^2 u. We then need to find dx in terms of du. Differentiating x=sec u gives us dx=secutanu du. Make this substitution and remember to change the limits
5. (Original post by warkan)
U mean sec^2x= 1+tan^2x ? Why do you need that here? Cant you just integrate Sec^2x directly?
if you were just integrating sec^2(x) then yes, but you're not.

How about you make the substitution (using integration by substitution) and see what it looks like, then use the identity sec^2(x)-1 = tan^2(x).
6. (Original post by JoMo1)
if you were just integrating sec^2(x) then yes, but you're not.

How about you make the substitution (using integration by substitution) and see what it looks like, then use the identity sec^2(x)-1 = tan^2(x).

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