Mathematics : Coordinate Geometry: Points to Remember: Equation, Formulas, forms

**Points to
Remember**

·
The
area of a triangle formed by the points *(x _{1}
, y_{1} ) , (x_{2} , y_{2} ) and (x_{3} , y_{3}
)* is

·
Three
points *A*(*x*_{1},*y*_{1}),B(x_{2},y_{2})
and C(x_{3},y_{3}) are collinear if and only if

(i)
area of ΔABC = 0 or *x _{1}y_{2}
+ x_{2}y_{3} + x_{3}y_{1} = x_{2}y_{1}
+ x_{3}y_{2} + x_{1}y_{3}*

(ii)
slope of AB = slope of BC or slope of AC

·
The
area of a quadrilateral formed by the four points *(x _{1}
, y_{1} ) , (x_{2} , y_{2} ), (x_{3} , y_{3}
) and (x_{4} , y_{4} )*is

·
If
a line makes an angle θ with the positive direction of X axis, then its slope *m* = tanθ.

·
If
A(*x _{1},y_{1}*), B(

·
Slope
of line *ax+by+c*= 0 is m = − *a/b*.

**Equation of straight line in various
forms**

·
Two
straight lines are parallel if and only if their slopes are equal.

Tags : Coordinate Geometry | Mathematics Coordinate Geometry | Mathematics

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