MYP Standard Mathematics Right Triangles and Circle Geometry Key Definitions

An angle formed when two lines from a point meet two points on a circle. For example, chord $AC$ subtends an angle at the center $\angle AOC$ and an angle at the circumference $\angle ABC$.

A part of the circumference of a circle between two points.

The point inside a circle that is the same distance from every point on the circumference.

A line segment joining two points on the circumference of a circle.

The curved boundary (perimeter) of a circle.

A statement formed by switching the “if” part and the “then” part of a conditional statement.

For an acute angle $A$ in a right triangle, $\cos A=\dfrac{\text{adjacent}}{\text{hypotenuse}}$.

A quadrilateral whose vertices all lie on the circumference of the same circle.

A chord that passes through the center of the circle, its length is twice the radius.

The side opposite the right angle in a right triangle, always the longest side.

In any right triangle, the squares of the two shorter sides add to the square of the hypotenuse: $a^2+b^2=c^2$.

A line segment from the center of a circle to a point on the circumference.

A triangle with one angle equal to $90^\circ$.

A line that intersects a circle at two points.

The region bounded by two radii and the arc between them (a “pizza slice”).

The region bounded by a chord and the arc between the chord’s endpoints.

For an acute angle $A$ in a right triangle, $\sin A=\dfrac{\text{opposite}}{\text{hypotenuse}}$.

For an acute angle $A$ in a right triangle, $\tan A=\dfrac{\text{opposite}}{\text{adjacent}}$.

A straight line that touches the circle's circumference at exactly one point, called the point of tangency, without crossing into the interior