Angles, lines and polygons Flashcards
What angle is a full turn?
360°
What angle is a half turn?
180°
What angle is a right angle?
90°
What is an obtuse angle?
(90°, 180°)
What is an acute angle?
(0°, 90°)
What is a reflex angle?
(180°, 360°)
If two straight lines pass through each other and you know one angle is a°, what are the other angles?
The angle opposite will also be a°. Then, to find the other angles, you can do 180° - a° to know both of the other angles.
If a line passes through a set of parallel lines, and we say the angles around each intersection is a, b, c, d, e, f, g, h from top to bottom, and we know the value of a, how do we find the other angles?
a = e which in turn means that a = d = h = e. Then, we can say that b = 180° - a. Therefore overall we can state that a = d = e = h and 180° - a = b = c = f = g.
What is an Equilateral triangle?
A triangle with three equal sides and three 60° angles.
What is an Isosceles triangle?
A triangle with two equal sides and two equal angles.
What is a Right-angled triangle?
A triangle with a right angle.
What is a Scalene triangle?
A triangle that isn’t Isosceles.
What do all the angles in triangles add up to?
180°, because if you draw a line parallel to the base of the triangle at the top, then the parallel line laws state that the angles in a triangle must add up to 180°.
What is a square?
A quadrilateral that has four equal sides and four 90° angles.
What is a rectangle?
A quadrilateral that has four 90° angles.
What is a rhombus?
A quadrilateral that has four equal sides.
What is a parallelogram?
A quadrilateral that has two pairs parallel lines.
What is a trapezium?
A quadrilateral that has one pair of parallel lines.
What is a kite?
A quadrilateral that is not a square, but has diagonals that bisect at right angles.
What is a polygon?
A straight lines, closed, 2D shape with at least three sides.
What is a regular polygon?
A polygon with equal sides and equal angles.
What is an irregular polygon?
A polygon that isn’t regular.
How can you find what the sum of the interior angles of a polygon should be?
By splitting the shape into triangles and seeing how many make up the whole shape. Then, multiply 180° by the number of triangles.
What do the exterior angles of a polygon always add up to?
360°
What is a line of symmetry?
When the shape can be folded along that line and all of the edges match up.
In a regular polygon, what is the rule for the rotational symmetry?
The number of lines of symmetry equal the number of sides.
What is rotational symmetry?
If it can be rotated and still look the same.
What is the rule for the order of rotational symmetry in a regular polygon?
The order of rotational symmetry equals the number of sides.
