An obtuse angle is greater than 90° but less than 180°

A reflex angle is greater than 180° but less than 360°

Angles on a straight line add up to how many degrees?

Angles around a point add up to how many degrees?

Two angles on a straight line are 115° and x°. Find x.

Three angles around a point are 90°, 140°, and x°. Find x.

When two lines cross, the angles opposite each other are equal

Two lines cross. One angle is 70°. What is the vertically opposite angle?

Angles in a triangle add up to how many degrees?

A triangle has angles of 50° and 70°. What is the third angle?

What is each angle in an equilateral triangle?

An isosceles triangle has one angle of 40°. The 40° is not between the equal sides. Find the other angles.

Angles in a quadrilateral add up to how many degrees?

Three angles of a quadrilateral are 85°, 90°, and 110°. Find the fourth angle.

Sum of interior angles = (n - 2) × 180° where n is the number of sides

What is the formula for the sum of interior angles in a polygon?

What is the sum of interior angles in a pentagon (5 sides)?

What is each interior angle of a regular hexagon?

Exterior angles of any polygon add up to how many degrees?

What is each exterior angle of a regular octagon (8 sides)?

When a line crosses two parallel lines, alternate angles are equal and form a Z shape

When a line crosses two parallel lines, corresponding angles are equal and form an F shape

What are corresponding angles (F-angles)?

When a line crosses two parallel lines, co-interior angles add up to 180°

What are co-interior angles (C-angles or allied angles)?

A transversal crosses parallel lines. One angle is 65°. What is the corresponding angle?

A transversal crosses parallel lines. One co-interior angle is 110°. What is the other?

A regular hexagon has 6 lines of symmetry

How many lines of symmetry does a regular hexagon have?

What is the order of rotational symmetry of a regular pentagon?

The ratio of angles in a triangle is 2:3:4. Find the largest angle.

An exterior angle of a regular polygon is 30°. How many sides does it have?

Find angle x: Triangle ABC where angle A = 40°, angle B = 60°, and x is an exterior angle at C.

Learn angle types, properties of shapes, and geometric reasoning