Set p can be regarded as a trajectory figure of an equicircular motion with (cosa, sina) as the center and radius of 2.
The combination of numbers and shapes, the viewpoint of movement change.
Set p can be regarded as a trajectory figure of an equicircular motion with (cosa, sina) as the center and radius of 2.
That is, the set P can be regarded as an isocircular curve package with the center moving on the upper half unit circle and the radius of 2.
Consider several special circles.
(ten1) 2+y 2 = 4, x 2+(y-1) 2 = 4.
Visible clues.
The whole image is similar to an inverted "?" Form. As shown in the figure.
Its area, the upper part of the X axis is equal to the semicircle X 2+Y 2 = 9 (Y >); =0)
The lower part of the x axis is equal to two semicircles (x1) 2+y 2 = 4 (y