Although Excel can't calculate the exact area under a curve, which requires the use of integral calculus, you can still use it to get a very close approximation. Excel approximates the area under a curve using the "trapezoid rule" method, which is the method math student who haven't yet learned calculus use to approximate the area under curves.

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Open Microsoft Excel, select the "Folder" icon and search for an existing file that contains data you've already graphed. Alternatively, input your "x" coordinates into cells in column "A" and "y" coordinates into corresponding cells in column "B." Click the "Graphs" button and choose the "Line Graph" option.

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Click your mouse inside the "C" cell next to the first set of "(x,y)" coordinates. For example, if these are cells A3, B3 and C3, type the following formula into the cell:

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\=(B4+B3)/2*(A4-A3)

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Click the "C" cell again, then drag the black box that appears around it down to the bottom of the last row of the data set, which applies the same formula to all the "C" cells. Click the mouse inside the "C" cell below the last row of the data set and type in the following formula:

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\=SUM(C3:C8)

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This assumes that the data begins in row "3" and ends in row "8." The resulting integer is the area under the curve.