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Mathematics 7 Online
OpenStudy (helpmeeplz):

Calculus help plz!

OpenStudy (helpmeeplz):

OpenStudy (helpmeeplz):

@mrm

OpenStudy (mrm):

alright, let me take a look at it

OpenStudy (helpmeeplz):

@AloneS

myininaya (myininaya):

do you know that \[\int\limits g'(x) dx= g(x)+C \\ \] and also that \[\int\limits_a^b g'(x) dx=g(x)|_a^b =g(b)-g(a)\]

OpenStudy (helpmeeplz):

how do i apply this to my problem?

myininaya (myininaya):

\[\text{ Let } F(x)=\int\limits_1^x g'(t) dt \\ \text{ Then we can write } F(x)=g(t)|_1^x \\ \text{ which means } F(x)=g(x)-g(1)\]

myininaya (myininaya):

now to find the derivative of F just differentiate both sides

myininaya (myininaya):

\[F(x)=\int\limits_1^x g'(t) dt \implies F'(x)=g'(x)\]

myininaya (myininaya):

this is one of the fundamental theorems of calculus

OpenStudy (helpmeeplz):

im still a little confused. can you keep helping me?

myininaya (myininaya):

may i ask what part what I said is confusing so i can explain that part more

OpenStudy (helpmeeplz):

what am i taking the derivative of?

myininaya (myininaya):

you are taking the derivative of F aka the derivative of the integral

OpenStudy (helpmeeplz):

with the limits?

myininaya (myininaya):

yes your integral has limits

myininaya (myininaya):

the lower limit is x^3 while the upper limit is 1

myininaya (myininaya):

can you tell me if you understand everything I said above?

OpenStudy (helpmeeplz):

yes, but i cant take the derivative of it with t

myininaya (myininaya):

\[F(x)=\int\limits_1^x g'(t) dt= g(t)|_1^x =g(x)-g(1)\] so you understood this?

OpenStudy (helpmeeplz):

no

OpenStudy (mrm):

Sorry, I lost your question Help. You're in good hands with myininaya.

myininaya (myininaya):

do you know to find a definite integral you must find an antiderivative of the integrand an antiderivative of g'(t) is g(t)

myininaya (myininaya):

however what I'm trying to show is you don't actually need to know the antiderivative to find the derivative of a definite integral that is in terms of x

myininaya (myininaya):

like here is another example: \[F(x)=\int\limits_{x^2}^{1} g'(t) dt= g(t)|_{x^2}^{1}=g(1)-g(x^2) \\ \text{ now \to find } F' \\ \text{ I differentiate both sides of } F(x)=g(1)-g(x^2)\]

myininaya (myininaya):

\[F'(x)=0-(x^2)' \cdot g'(x^2) \\ F'(x)=-2x g'(x^2)\]

myininaya (myininaya):

g'(x^2) can be evaluated easily since you know what g'(t) equals this was the integrand

myininaya (myininaya):

can you try yours forgot about cos(t^4) for a sec and replace it with g'(t)

myininaya (myininaya):

and follow what I did above except with your limits

OpenStudy (helpmeeplz):

i will try

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