Area: Triangle

Triangle: area

Triangle area (different basis)

Triangles area: parallel lines

Triangle area (same base)

Triangle area: same base & height

Area: Parallelogram (same sides not equal area)

Area: parallelogram to rectangle

Area: parallelogram (triangles)

Area: parallelogram (between parallel lines)

Area: parallelogram (parallel lines)

Area: KISS

Alternate angles

Alternate angles

Co-interior angles

Alternate angles

Co-interior angles

Drag the points

Corresponding angles

Drag the points

Vertical opposite angles

Angles on a straight line

Geometry: radius of the earth

Geometry: radius of the earth (large)

Sum of the interior angles

Exterior angle of a triangle

Equilateral triangles

Isosceles triangles

Right-angled triangle

Triangle area (different basis)


Congruent: triangles

Congruent: triangles

Triangle sides: midpoints

Points of intersection (Euler line)


Trapezium (trapezoid)






Quadrilateral: properties

Trapezium: properties

Parallelogram: properties

Rhombus: properties

Square: properties

Drag the vertices of the square. What do you notice?

Kite: properties

Rectangle: properties

Parrallelogram inside a quadrilateral