AP® Calculus BC · Unit 8 · Topic 8.8

Volumes with Cross Sections: Triangles and Semicircles

Watch it explained

  1. How it worksHow does a semicircle standing on a chord turn into π over 8 times that chord squared?
  2. Worked exampleFind the volume of a solid with equilateral triangle cross sections over the region under y = 4 - x2.
  3. Common mistakeWhy doesn't the semicircle's radius equal the full distance between the two curves?
  4. Going furtherWhat happens to the volume formula when the cross sections are isosceles right triangles?

Check yourself

Your turn1 of 2
Find the volume of a solid with equilateral triangle cross sections standing on the region under y = 5 - x2 (down to the x-axis).

End of topic.