In RT △ ABC, AC = 3cm, BC = 4cm, ab = 5cm, take the line segment of the three sides as the axis of rotation respectively, and get the relationship of the three geometric bodies after one revolution?

In RT △ ABC, AC = 3cm, BC = 4cm, ab = 5cm, take the line segment of the three sides as the axis of rotation respectively, and get the relationship of the three geometric bodies after one revolution?

If the height on the right edge is higher and ab intersects with D, then CD = AC * BC / AB = 12 / 5, the volume of geometry around AC = 1 / 3 * pi * BC * BC = 1 / 3 * pi * 4 * 4 * 3, the volume of geometry around BC = 1 / 3 * pi * ac * ac * BC = 1 / 3 * pi * 3 * 4, the volume of geometry around AB = 1 / 3 * pi * CD * CD * ad + 1 / 3 * pi * CD * CD * BD = 1 / 3

It is known that in RT △ ABC, ∠ ACB = 90 ° and CD is the height on the edge of AB, ab = 13cm, BC = 12cm and AC = 5cm

S△ABC=12*5/2=30CM^2
So CD = 30 * 2 / 13 = 60 / 13cm
A: the area of △ ABC is 30cm ^ 2, and the length of CD is 60g13cm

If AB = 15cm, BC = 5cm, then the length of AC is equal to (). A. 20cm or 10cm. B. uncertain

When a, B and C are in a straight line, the length of AC is 20cm or 10cm
When a, B and C are not in a straight line, the AC length cannot be determined
Therefore, choose B