1. First, we need to find the minimum positive period of this function: 2π/2=π. That is, π is the minimum positive period of a function.

2. Divide the minimum positive period into four equal parts, that is, divide the interval of π into: 0, π/4, π/2, 3π/4, π.

3. Calculate the sine values of the above five endpoints: sin2*0= 1, sin2*π/4= 1, sin2*π/2=0, sin2*3π/4=- 1, sin2*π=0.

4. Find five points, namely: (0,0) (π/4, 1) (π/2,0) (3 π/4,1) (π, 0).

5. Connect five points with a smooth curve to get an approximate image of sin2x in the minimum positive period. The figure shows the final connection diagram.

Definition of unit circle

A common angle in radians is given in the image. The counterclockwise measurement is a positive angle, and the clockwise measurement is a negative angle. Let a straight line passing through the origin make an angle θ with the positive half of the X axis and intersect the unit circle. The y coordinate of this intersection is equal to sinθ.

The triangle in this figure guarantees this formula; The radius is equal to the hypotenuse and the length is 1, so there is sinθ=y/ 1. The unit circle can be regarded as a way to view infinite triangles by changing the lengths of adjacent sides and opposite sides and keeping the hypotenuse equal to 1. That is, sinθ=AB, which is positive when it is in the same direction as the positive direction of the Y axis, otherwise it is negative.

For angles greater than 2π or less than 0, just keep rotating around the unit circle. In this way, sine becomes a periodic function with a period of 2π.