Math CentralQuandaries & Queries


Question from Linda, a parent:

How do you calculate the volume of a cone that is 25cm high and has an angle of 20 degrees?

Hi Linda,

The volume of a cone of base radius $r$ cm and height $h$ cm is

\[\frac13 \pi\; r^2 h.\]

You know the height so you need to find the radius of the base.


In my diagram the triangle ABC is a right triangle and the measure of angle CAB is 20 degrees. What trig function connects the lengths of the sides BC and CA with the measure of the angle CAB?


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