Download 2-D Geometry Terms

2-D Geometry Terms
Opposite side – In a triangle, the side that is not one of the two rays making the
angle.
Parallel – Lines that will never intersect.
Line of symmetry – A line that will separate a shape into two identical halves.
Acute Angle – Less that 90 degrees.
Obtuse Angle – Greater than 90 degrees.
Right Angle – 90 degrees exactly.
Kite – A quadrilateral that has two pairs of equal sides with no sides parallel.
Parallelogram
A 4-sided flat shape with straight sides where opposite sides are parallel.
Also:
* opposite sides are equal in length, and
* opposite angles are equal (angles "a" are the same, and angles "b" are the same)
NOTE: Squares, Rectangles and Rhombuses are all Parallelograms!
Rectangle
A 4-sided flat shape with straight sides where all interior angles are
right angles (90°).
Also opposite sides are parallel and of equal length.
Example: A square is a special type of rectangle.
Square
A 4-sided flat shape with straight sides where:
* all sides have equal length, and
* every angle is a right angle (90°)
It is a Quadrilateral and a Regular Polygon
Rhombus
A Rhombus is a flat shape with 4 equal straight sides.
A rhombus looks like a diamond
Quadrilaterals
Quadrilateral just means "four
sides"
(quad means four, lateral means
side).
Any four-sided shape is a
Quadrilateral.
But the sides have to be straight,
and it has to be 2-dimensional.
Trapezoid
A trapezoid is a 4-sided flat shape with straight sides that has a pair of opposite
sides parallel.
Trapezoid
Isosceles Trapezoid
Types of Triangles
(3 sided shapes with 3 internal angles that add up to 180 degrees)
Equilateral Triangle: All Three Sides Are Congruent.
Isosceles Triangle: Two Sides Are Of Equal Length.
Scalene Triangle: No Sides Are Congruent
Right Triangle: One Angle Is A Right Angle.
Acute Triangle: All Angles Are Acute.
Obtuse Triangle: One Angle is An Obtuse Angle.
Pythagorean Theorem
In a right angled triangle the square of the long side is equal to the sum of the
squares of the other two sides.
It is stated in this formula:
a2 + b2 = c2
Majority of Information sourced from: http://www.mathsisfun.com/geometry/