Area of a circle
Arcs
Sectors
Segments
Triangles
When a triangle is incribed in a rectangle of height h and width b, the perpendicular divides the shape. It can be seen that each rectangle formed is composed of two triangles of equal area. Hence the area of the original triangle is half that of the rectangle.
The expression containing the sine is really the same as above.
Parallelograms
Trapeziums
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