Notes on Geometry

AcuteAngles

An angle that is less than 90 degrees.Angles

RightAngles

An angle that equals 90 degrees.Angles

ObtuseAngles

An Angle that is more than 90 degrees.Angles

Straight anglesAngles

An angle that equals 180 degrees.Angles

ComplementaryAngles

Two angles that add up to 90 degrees.Angles

supplementaryAngles

Two angles that measure up to 180 degrees.Angles

parallelAngles

Two lines that never touch.Angles

Corresponding anglesAngles

Are equal! They are the matching angles when a parallel line is crossed with a third line. (so, for example, angle 1 and angle 2 are corresponding angles.)Angles

1

2

How many degrees are in a triangle?Triangles

180 degrees in every triangle.Triangles

isoscelesTriangles

A triangle with two equal sides.Triangles

equilateralTriangles

All the sides are equal.Triangles

scaleneTriangles

No sides are equalTriangle

rightTriangles

A triangle with one right angle.Triangles

ObtuseTriangles

A triangle with one obtuse angle.Triangles

acuteTriangles

A triangle with all angles that are acute.Triangles

PolygonShapes

A shape with all straight sides.Shapes

Regular PolygonShapes

All equal angles and all equal sides.Shapes

QuadrilateralShapes

Shape with 4 sidesShapes

PentagonShapes

A shape with five sidesShapes

HexagonShapes

A shape with six sides.Shapes

HeptagonShapes

A shape with seven sides.Shapes

OctagonShapes

A shape with eight sides.Shapes

NonagonShapes

A shape with nine sides.Shapes

DecagonShapes

A shape with ten sides.Shapes

ParallelogramShapes

A quadrilateral with two sets of parallel sides.

TrapezoidShapes

A quadrilateral with only ONE set of parallel sides.

RectangleShapes

A parallelogram with 90 degree angles.Shapes

SquareShapes

A rectangle with all equal sides. (90 degree angles).

Area of a parallelogramShapes

Base * heightShapes

Area of a triangleShapes

½ base*height

Area of a circleShapes

A = pi*r-squaredShapes

CircumferenceShapes

Perimeter of a circleC=diameter * piShapes