 3rd Grade - Geometry

# 4 - Geometry

Here are few notions of geometry you should know...

## Straight lines, semi-straight lines, and segments

 The straight line The segment The semi-straight line   A straight line is a line with no beginning and no end, and therefore infinitely long. A segment is a line with two boundaries (or vertices). A semi-straight line is a line which has a boundary (or vetex) on one side and is infinite on the other side.

## Angle

An angle is formed by two semi-straight lines with same vertex . ## Straight angle

A right angle is an angle which has the same shape as angles in squares or rectangles. ## Parallel, perpendicular lines

Two straight lines are parallel if they never intersect.
Two straight lines are perpendicular if they intersect with a right angle.
 The yellow lines are parallel the green lines are perpendicular ## The parallelogram

 A parallelogram is a 4-edges figure with parallel opposite edges. ## Some triangles

 Right-angled triangle Isosceles triangle Equilateral triangle   A right-angled triangle is a triangle with a right angle An isosceles triangle is a triangle with two edges of the same length An equilateral triangle is a triangle with three edges of the same length