Geometric significance and application scope of formal constant of name equation
Point-oblique type
Y-y 1 = k (x-x1) (x1,y1) is a fixed point on a straight line, and k exists.
A straight line that is not perpendicular to the x axis
slope intercept form
Y = kx+b k is the slope, and b is the intercept of a straight line on the y axis.
A straight line that is not perpendicular to the x axis
Two-point formula y-y1y2-y1= x-x1x 2-x1.
(x 1≠x2，y 1≠y2
(x 1, y 1) and (x2, y2) are two fixed points on a straight line.
A straight line that is not perpendicular to the x and y axes.
Intercept xa+Yb = 1
(a, b ≠ 0) A is the non-zero intercept of a straight line on the X axis, and B is the non-zero intercept of a straight line on the Y axis, which is not perpendicular to the X and Y axes, but just the origin.
general formula
Ax+By+C=0
The slope of (A2+B2 ≠ 0) is -AB, the intercept on the X axis is -CA, and the intercept on the Y axis is -CB.
A straight line at any position
1, definition of circle, standard equation, (x-a) 2+(y-b) 2 = R2; Parametric equation:
2. General equation of circle: x2+y2+Dx+Ey+F=0? The formula has a center (-D2, -E2) with a radius of12d2+E2-4f; It reflects its algebraic characteristics: ①x2+y2 coefficients are the same and both are 1, ② X-free? Project y