THEME 2

DEFINITIONS ANGLE: the amount of turn between two straight lines that have a common end point

VERTEX: the common endpoint between two straight lines

DEGREE(S): a measure unit for angles

RIGHT ANGLE: a 90° angle

ACUTE: an angle less than 90°

OBTUSE ANGLE: an angle that is greater than 90°

ADJACENT: ‘next to’ ADJACENT ANGLE: angles that are next to each other

OPPOSITE ANGLES: angles that are across the vertex from each other when two lines cross

INTERSECTING: crossing over

180. / equals / 3 / angles / a / sum / triangle's / The / always / of Sentence Jumble! The sum of a triangle’s 3 angles always equals 180.

Example Problem A A triangle has an obtuse angle that measures 116 ∘. The lines extending from the vertex of that angle are both the same length, so the other two angles of the triangle are equal to each other. What is the measure of each one?

Example Problem B Think of a clock’s face. It shows that it is 10:30. What is the angle between the hour hand and the minute hand?