Cut a sector with a center angle of 120 ° from a circular plate with a radius of 12cm, and use it to make a funnel to find the height of the funnel?

Cut a sector with a center angle of 120 ° from a circular plate with a radius of 12cm, and use it to make a funnel to find the height of the funnel?

Let H be the height of the funnel and R be the bottom radius of the funnel
It can be seen from the question that the circumference of the funnel ground is the arc length of the sector
Then (120 / 360) * 2 * Pai * 12 = 2 * Pai * r, that is, r = 4cm
And the radius of the circular plate, that is, the length of the oblique line of the funnel, is obtained from the Pythagorean theorem
H = change number (12 * 12-4 * 4)