Univariate quadratic equation ax? +bx+c=0

If there is a solution, the relationship between the two roots is: x1+x2 =-b/ax1x2 = c/a.

slanting

The straight line y=k 1x+b is perpendicular to y = k2x+b.

Then K 1*K2=- 1.

The straight line y=k 1x+b is parallel to y = k2x+b.

Measure k 1=k2.

The intersection of the centerline divides the centerline into two short segments of 2: 1.

Intersecting chord theorem: the product of the length of two intersecting chords and two straight lines divided by the intersection point in a circle.

Equality.

Secant theorem: the tangent and secant of a circle are drawn from a point outside the circle, and the length of the tangent is the middle term in the length ratio of the two lines where this point intersects the secant.

Chord tangent angle theorem: the chord tangent angle theorem is equal to the circumferential angle of the arc pair it clamps.

Tangent Length Theorem: Two tangents leading to a circle from a point outside the circle are equal in length, and the connecting line between the center of the circle and this point bisects the included angle of the two tangents.

Triangle area algorithm

S=0.5*ab*sinc

Helen formula √[p(p-a)(p-b)(p-c)], p=(a+b+c)/2.

Abc is three-sided. This formula knows that three sides can find the area, but the operation is complicated.

Quadrilateral theorem inscribed in a circle

Tangent secant theorem

Tangent theorem

Archimedes' broken line theorem

secant theorem