# Plane figures, angle

Classified in Mathematics

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A parallelogram is a quadrilateral with two pairs of parallel sides. You can choose any side to be the base. An altitude is any segment perpendicular to line containing the base drawn from the side opposite the base. The height is the **length** of an altitude.

Area of Rectangle= A = bh

Area of a parallelogram = A = bh

Area of a triangle = 1/2bh

Area of a trapezoid = A = 1/2h(b1 + b2)

Area of a rhombus or a kite = A = 1/2 d1d2

Area of a regular polygon = A = 1/2ap - apothem, perimeter

If the scale factor of 2 similar figures is a/b then the ratio of their perimeters is a/b and the ratio of their areas is a^2/b^2

Arc

**measure**- The measure of a minor**arc**is equal to the measure of its corresponding central angle. The measure of a major arc is the measure of the related minor arc subtracted from 360. The measure of a semicircle is 180.Arc addition postulate - The measure of the arc formed by two adjacent arcs is the sum of the measures of the two arcs.

Circumfrence of a

**circle**- C = pid or C = 2pirArc Length - the length of an arc of a circle is the product of the ratio, measure of arc/360 and the circumfrence of the circle. Length of AB = mAB/360 * 2pir, or mAB/360 * pid

Area of a circle - A = pir^2

Area of a sector of a circle- mAB/360 *pir^2