It can be understood that the coordinates are known. Draw a circle with 1 as the center on the X axis and Y axis. Let the angle between the ray and the X axis from the origin be θ, the intersection of the ray and the circle be A, and let the coordinate of A be (a, b). At this time, sin θ = b, cos θ = a, and tan θ = b/a.

When the angle θ is greater than 90 degrees and less than 180 degrees, it is obvious that a

When θ=90 degrees, the intersection point is (0, 1), so sin90 degrees = 1, cos90 degrees =0, tan90 degrees = 1/0, infinity.

When θ=0 degrees, the intersection point is (1, 0), so sin0=0, cos0= 1, tan0 = 0= 0;

When θ= 180 degrees, the intersection point is (-1 0), so sin 180 degrees =0, cos 180 degrees =- 1, tan 180 degrees =