Google Classroom
GeoGebraGeoGebra Classroom

Volume of revolution

Task

The volume of a glass can be formed by rotating the function (x, f(x) in cm) around the y-axis. The volume of the glass should be 500 ml. Estimate the height of the glass. Hint: Use the formula to calculate the volume of revolution around the y-axis of the portion of f(x) in the y-interval [a, b].

Explore the construction...

Instructions

1.Enter the function into the Input Bar and press Enter.
Note: The graph of f(x) will be displayed in the Graphics View.
2.Calculate the inverse of f(x) using the command .
3.Press the More button and select Add label to label the inverse of f(x) with g.
4.Use the formula from the hint to calculate the volume of revolution around the y-axis of f(x) in the y-interval [0,h], where h is the height of the glass.
Enter the command into the Input Bar and press Enter.
5.As the volume should be 500 ml, solve the equation .
Therefore use the label you gave to the Integral and enter the command .
6.Press the numeric toggle button to show the numeric solution. As result, the height of the glass is about 13.16 cm.
Note: It is also possible to use more commands in one input. For example Steps 4 and 5 can be done by entering . GeoGebra CAS Calculator will automatically add a right parenthesis ) when entering your command with a left parenthesis (.

Try it yourself...