Find the perimeter of inscribed regular decagon with radius of 10cm

Find the perimeter of inscribed regular decagon with radius of 10cm

Side length = 2 * 10sin180 / 10 = 20 * sin18
Perimeter = 10 * 20 * sin18 = 200sin18

Let the radius be 10 cm, the radius be increased by 10 times, the diameter be increased by how many times, the perimeter be increased by how many times, and the area be increased by how many times

Analysis: according to the formula, diameter d = 2R, perimeter C = 2 π R, area s = π R ^ 2
The radius, diameter, perimeter and area will increase 10 times, 10 times and 100 times respectively

The circumference of a hula hoop is 376.8cm. How to calculate the enclosed area?

The radius is 376.8 ﹣ 2 ﹣ 3.14 = 60cm
The enclosed area is 3.14 × 60 × 60 = 11304cm and 178;