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# C4 Formula for calculating area under a curve Watch

1. ∫y dx/dt

When attempting to calculate the area under a curve. Do you always use the above formula? Or are there exceptions? Because I am sure I learnt a different formula in C2, just can't remember

Thanks
2. Most often you will need
3. Not sure if I've grasped what you're asking...
You use the equation of the curve you are integrating. It depends if the equation is or as to whether you use or .
4. (Original post by BabyMaths)
Most often you will need
HOw do you know whether to apply the above formula, or the one I gave? Thanks
5. (Original post by sabre2th1)
HOw do you know whether to apply the above formula, or the one I gave? Thanks
I think you meant . This is handy when you have parametric equations.
6. Given a function f(x), the notation:

Is more or less equivalent to saying: "A is equal to the sum of the values of f(x) over all values of x between b and c"

In other words, A is the area under the curve y = f(x) between the values x = b and x = c.

(EDIT: assuming the curve does not cross the x-axis.)
7. (Original post by james.h)

Is equivalent to saying: "A is equal to the sum of the values of f(x) over all values of x between b and c"
Kind of a dodgy definition don't you think?
8. (Original post by BabyMaths)
Kind of a dodgy definition don't you think?
Implicitly assumed here are that the "function" is "nice" (continuous, piecewise finite, &c).

...Okay, fine, but it gets the general idea across.

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