In Coordinate Geometry, we use graphs and coordinates to find measurements of geometric figures.

- Distance PQ =
- Slope of PQ = m =
- Equation of or y = mx + c
- The product of the slopes of two perpendicular lines is –1.
- The distance between the points (x
_{1}, y_{1}) and (x_{2}, y_{2}) is - If point P(x, y) divides the segment AB, where A ≡ (x
_{1}, y_{1}) and B ≡ (x_{2}, y_{2}), internally in the ratio m: n, then,

x= (mx_{2}+ nx_{1})/(m+n)

and

y= (my_{2}+ ny_{1})/(m+n) - If P is the midpoint then,
- If G (x, y) is the centroid of triangle ABC, A ≡ (x
_{1}, y_{1}), B ≡ (x_{2}, y_{2}), C ≡ (x_{3}, y_{3}), then,

x = (x_{1}+ x_{2 }+ x_{3})/3 and y = (y_{1}+ y_{2}+ y_{3})/3 - If I (x, y) is the in-centre of triangle ABC, A ≡ (x
_{1}, y_{1}), B ≡ (x_{2}, y_{2}), C ≡ (x_{3}, y_{3}), then, where a, b and c are the lengths of the BC, AC and AB respectively. - The equation of a straight line is y = mx + c, where m is the slope and c is the y-intercept (tan θ = m, where θ is the angle that the line makes with the positive X-axis).