In the plane rectangular coordinate system, for a straight line intersecting with the axis, if the axis rotates counterclockwise around the intersection point and the straight line coincides, the smallest positive angle is recorded as the inclination angle of the straight line. When the straight line coincides or is parallel to the axis, the specified inclination angle is 0;

2. Slope: If the inclination of the straight line is known to be 0 and 90, then the slope k=tan.

The slope of the straight line passing through two points (X 1, Y 1) and (X2, Y2) is k=( y2-y 1)/(x2-x 1), and the slope of the tangent line is obtained.

3. Straight line equation: (1) point oblique type: if the slope of the intersection of straight lines is 0, then the straight line equation is 0.

⑵ Oblique intercept type: If the intercept of a straight line on the axis is sum slope, the straight line equation is

4、 , ,① ∥ , ; ② .

The relationship between straight lines:

(1) Parallel A 1/A2=B 1/B2 Attention test (2) Vertical A 1A2+B 1B2=0.

5. Distance formula from point to straight line;

The distance between two parallel lines and is

6. Standard equation of circle: .2 General equation of circle:

Note that the standard equation can be transformed into a general equation.

7. A circle must have two tangents outside the circle. If only one tangent is found, the other tangent is a straight line perpendicular to the axis.

8. The positional relationship between a straight line and a circle is usually transformed into the relationship between the center distance and the radius, or a right triangle is constructed by using the vertical diameter theorem to solve the chord length problem. ① Separation ② Tangency ③ Intersection.

9. When solving the relationship between a straight line and a circle, we should give full play to the plane geometric properties of the circle (such as radius, half chord length and chord center distance to form a right triangle), and the chord length obtained by the intersection of a straight line and a circle.