A point on a straight line that is not parallel to the plane is regarded as the vertical line of the plane, and the intersection of this straight line and the plane and the intersection of the original straight line and the plane are composed of the original straight line (the complementary angle line plane of the included angle between this straight line and the original straight line), which is the included angle.

Angle range: [0,90] or [0,π/2]

Extended data:

Common units of measurement for angles

Draw an arc with the endpoint of the angle as the center. Since the radius of the arc is proportional to the length of the arc and the angle is proportional to the length, the size of the circle will not affect the measurement of the angle.

1, radian: the length of the arc cut by the angle on the circle is divided by the radius of the circle, which is generally recorded as rad. The radian is the unit of measurement of the angle stipulated in the international system of units, but it is not the legal unit of measurement in China, and the angle is the legal unit of measurement in China. In addition, radian is also widely used in mathematics and trigonometry.

2. Angle: the length of the arc divided by the angle on the circle divided by the circumference of the circle and then multiplied by 360, which is generally marked as 0 and read as "degree". It used to be divided into 60 minutes or 3600 seconds. Angle has important applications in astronomy and global positioning system.

3. Gradient: it is the result of dividing the length of the arc cut by the angle on the circle by the circumference of the circle and multiplying it by 400.