Angles in Polygons & Parallel Lines (Edexcel IGCSE Maths A)

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  • What are vertically opposite angles?

    Vertically opposite angles are angles that are opposite to each other when two lines intersect. Vertically opposite angles are equal.

    Vertically opposite angles.
  • True or False?

    Angles around a point add up to 180°.

    False.

    Angles around a point add up to 360°.

  • Define an isosceles triangle.

    An isosceles triangle is a triangle with two sides of equal length and two angles of equal size.

  • What is an equilateral triangle?

    An equilateral triangle is a triangle with three sides of equal length and three equal angles.

  • True or False?

    The three interior angles inside any triangle add up to 180°.

    True.

    The three interior angles inside any triangle add up to 180°.

  • Define the term quadrilateral.

    A quadrilateral is a polygon with four sides.

  • True or False?

    The four interior angles inside any quadrilateral add up to 360°.

    True.

    The four interior angles inside any quadrilateral add up to 360°.

  • What is the sum of angles along a straight line?

    Angles along a straight line add up to 180°.

  • True or false?

    Opposite angles in a rhombus are equal.

    True.

    Opposite angles in a rhombus are equal.

  • True or false?

    A kite has two pairs of equal angles.

    False.

    A kite is a quadrilateral with one pair of equal angles.

  • What is a polygon?

    A polygon is a flat (plane) shape with n straight sides.

    E.g. a quadrilateral is a 4-sided polygon.

  • True or False?

    The sum of the exterior angles in any polygon always adds up to 360°.

    True.

    The sum of the exterior angles in any polygon always adds up to 360°.

  • True or False?

    The sum of an interior angle and an exterior angle at the same vertex on a polygon is equal to 180°.

    True.

    The sum of an interior angle and an exterior angle at the same vertex on a polygon is equal to 180°.

  • State the equation in terms of the number of sides of a polygon, n, for the sum of interior angles in a polygon.

    The equation in terms of the number of sides of a polygon, n, for the sum of interior angles in a polygon is:

    Sum of interior angles = 180 cross times open parentheses n minus 2 close parentheses.

  • What is a regular polygon?

    A regular polygon is a polygon where all sides are equal and all angles are equal.

  • True or False?

    An irregular polygon can have more than one side of the same length.

    True.

    An irregular polygon can have more than one side of the same length.

    It is an irregular polygon unless all sides are the same length and all angles are the same size, in which case it would be a regular polygon.

  • True or False?

    The sum of interior angles in a regular polygon is different to the sum of interior angles in an irregular polygon with the same number of sides.

    False.

    The sum of interior angles in a regular polygon is the same as the sum of interior angles in an irregular polygon with the same number of sides.

    The sum of interior angles is dependent on the number of sides.

    It is not dependent on whether the polygon is regular or irregular.

  • What are parallel lines?

    Parallel lines are lines that are always equidistant (i.e. the same distance apart) and never meet.

  • What is a transverse line?

    A transverse line is a straight line that extends across two parallel lines.

  • What are corresponding angles?

    Corresponding angles are equal angles in corresponding positions.

    Pairs of corresponding angles.
  • What are allied (or co-interior) angles?

    Allied (co-interior) angles are a pair of angles that are formed between a pair of parallel lines and a transverse line. Allied angles sum to 180o.

    Pairs of co-interior angles.
  • What angle fact is represented by the diagram below?

    Two side-by-side diagrams show intersecting lines with orange shapes on the left and green shapes on the right, illustrating geometric relationships.

    Alternate angles are equal angles.

    Two side-by-side diagrams show intersecting lines with orange shapes on the left and green shapes on the right, illustrating geometric relationships.
  • True or False?

    In an exam question involving the use of angle facts, you should state the appropriate angle fact as well as the size of the relevant angle.

    True.

    To get full marks in an exam you will need to write down the size of any angles that you have found but you will also need to give reasons.

    Make sure that you use the correct terminology for the different angle facts.

  • True or False?

    The circumference of a circle is the perimeter of the circle.

    True.

    The circumference of a circle is the perimeter of the circle.

    It is the length around the outside of the shape.

  • What is the name for the line of symmetry of a circle?

    A circle's line of symmetry is known as the diameter.

    A diameter of a circle is a line that touches the circumference at either end and passes through the centre of the circle.

  • How many sides does a decagon have?

    A decagon has 10 sides.

  • What are the defining properties of a parallelogram?

    A parallelogram is a quadrilateral with:

    • two pairs of equal, opposite angles,

    • and two pairs of opposite, parallel sides.

    (Each pair of opposite parallel sides are also of equal length.)

  • What are the defining properties of a rhombus?

    A rhombus is a quadrilateral with:

    • two pairs of equal, opposite angles,

    • two pairs of opposite, parallel sides,

    • and four sides of equal length.

  • True or False?

    The diagonals of a rectangle bisect each other at the centre of the rectangle.

    True.

    The diagonals of a rectangle bisect each other at the centre of the rectangle.

  • What are the defining properties of a trapezium?

    A trapezium is a quadrilateral with:

    • one pair of opposite, parallel sides of unequal length.

  • What are the defining properties of a kite?

    A kite is a quadrilateral with:

    • one line of symmetry,

    • one pair of equal angles opposite the main diagonal,

    • and two pairs of equal, adjacent sides.

  • True or False?

    The diagonals of a rhombus bisect each other at right angles (90°).

    True.

    The diagonals of a rhombus bisect each other at right angles (90°).

  • True or false?

    If a trapezium has a line of symmetry it is an isosceles trapezium.

    True.

    If a trapezium has a line of symmetry it is an isosceles trapezium.