Coordinate Geometry

Distance:

Distance between (x1,y1), (x2,y2)
= sqrt[(x2-x1)^2 + (y2-y1)^2]

Midpoint:

((x1+x2)/2, (y1+y2)/2)

Section formula:

Point dividing A(x1,y1), B(x2,y2) in ratio m:n internally:
((mx2 + nx1)/(m+n), (my2 + ny1)/(m+n))

Slope:

m = (y2-y1)/(x2-x1)
Parallel lines: slopes equal
Perpendicular lines: m1*m2 = -1

Line equation:

y = mx + c
y - y1 = m(x - x1)

Area of triangle:

Area = 1/2 * |x1(y2-y3) + x2(y3-y1) + x3(y1-y2)|

Circle:

(x-a)^2 + (y-b)^2 = r^2
Center = (a,b), radius = r

Coordinate Geometry​