Page 221 - ABCTE Study Guide_Neat
P. 221
A Isosceles, right
B Isosceles, obtuse
C Scalene, acute
D Scalene, right
Answer
The correct choice is B. This is an isosceles, obtuse triangle. The base angles are congruent, so we know
that the sides opposite those angles are also congruent, which makes this an isolsceles triangle. The
base angles each measure 40°, for a total of 80°. The sum of the angles in a triangle is 180°, therefore,
the vertex angle must measure 180° – 80°, or 100°. Thus, the triangle is obtuse. You cannot assume that
the vertex angle is a right angle, although it does look like one. Objects are often not drawn to scale.
Quadrilaterals
Quadrilateral literally means “four sides.” A quadrilateral is a four-sided polygon. This is the Quadrilateral
Family Tree.
