#### Topic: Area under a curve

Hi,

I have y = 3x^2 + 5 as the curve and points 2 and 6 on the x axis, BUT, given that this gives y = 13 and 117 respectively for those values. How can I calculate the area from the y axis ? (I know that x = sqrt((y-5)/3).

Pete

#### Re: Area under a curve

I think you mean that your points are (2,17) and (6,113). The easiest way to calculate the area between the function and the y-axis is to mirror the function as you have started to do. Plot the inverse function as f(x)=sqrt((y-5)/3) and calculate the area between it and the x-axis using Calc|Area from 17 to 113.

#### Re: Area under a curve

Ivan Johansen wrote:

I think you mean that your points are (2,17) and (6,113). The easiest way to calculate the area between the function and the y-axis is to mirror the function as you have started to do. Plot the inverse function as f(x)=sqrt((y-5)/3) and calculate the area between it and the x-axis using Calc|Area from 17 to 113.

I have plotted f(x)=sqrt((x-5)/3) (as opposed to using y), and get the answer I would expect, but is it possible to draw the graph and show the area from the y-axis ?

#### Re: Area under a curve

When you have plottet the function, you can use Function|Insert shading and choose Between function and y-axis. Under Options you can specify the range to be from 2 to 6.