Thanks for the reply, the information was useful. I decided to use the trapeziod method in determining the area under the curve and this is my result
x y= f(x) area
3.00 1.17
3.60 1.02 0.66
4.00 0.90 0.38
4.70 0.63 0.54
5.50 0.59 0.49
6.25 0.63 0.46
7.00 0.66 0.48
7.50 0.79 0.36
8.60 1.20 1.09
9.00 1.45 0.53
9.40 1.65 0.62
10.00 2.05 1.11
10.45 2.26 0.97
10.85 2.62 0.98
11.25 3.00 1.12
Area 9.79
the method used is trapezoidal approximation
to calculate the area increament by
(d8+d9)/2 * (c9 - c8).
but my question how would l plot a graph that would look like a curve. I went to chart wizard and clicked on area and column to plot a curve graph, but it did not give me what l needed. I even tried to join the two graph together, but all l get was just one graph. Moreover, l used the Visual basic editing on the tool bar, but my function keeps giving me errors. I know l am doing something wrong, which l cant't figure out.
Is there any clue to what l did wrong,thanks