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Shapes, angles and coordinates
Geometry questions use precise names. Knowing the properties of shapes and how coordinates work saves you time on almost every geometry topic.
Types of angle
Acute: less than 90°
Right angle: exactly 90°
Obtuse: more than 90° but less than 180°
Reflex: more than 180° but less than 360°
Right angle: exactly 90°
Obtuse: more than 90° but less than 180°
Reflex: more than 180° but less than 360°
Quadrilaterals
Each has its own properties.
Coordinates
Write (x, y): go across first, then up or down.
(−3, 4) is 3 left and 4 up from the origin.
The midpoint of two points: add the x-coordinates and halve, add the y-coordinates and halve.
Midpoint of (2, 5) and (8, −1) is ((2 + 8) ÷ 2, (5 + (−1)) ÷ 2) = (5, 2).
(−3, 4) is 3 left and 4 up from the origin.
The midpoint of two points: add the x-coordinates and halve, add the y-coordinates and halve.
Midpoint of (2, 5) and (8, −1) is ((2 + 8) ÷ 2, (5 + (−1)) ÷ 2) = (5, 2).
Find the midpoint of (−4, 3) and (6, 9).
- x: (−4 + 6) ÷ 2 = 1
- y: (3 + 9) ÷ 2 = 6
Answer: (1, 6)
Know the angle names by size. Learn the side, angle and diagonal properties of each quadrilateral. Coordinates go across then up; a midpoint is the mean of the x-values and the mean of the y-values.
The interactive lesson includes the diagrams for this topic.
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