Triangles • A triangle is a 3-sided polygon. Every triangle has three sides and three angles. When added together, the three angles equal 180°.
Acute Triangles • A triangle in which all three angles are less than 90°.
Obtuse Triangles • An obtuse triangle is a triangle in which one of the angles is greater than 90°.
Right Triangles • A right triangle is triangle with an angle of 90°.
Scalene Triangles • A triangle with three unequal sides.
Isosceles Triangles • An isosceles triangle is a triangle with (at least) two equal sides.
Isosceles Triangle Theorem • The following movie shows that if two sides of a triangle are congruent, then the angles opposite those sides are congruent.
Equilateral Triangles • An equilateral triangle is a triangle with all three sides of equal length.
Equiangular Triangles • An equiangular triangle is a triangle which has three equal angles.
Congruent Triangles • Congruent triangles are triangles whose corresponding angles and sides are congruent. • They are exactly the same size and shape.
The Hypotenuse • The hypotenuse of a right triangle is the triangle's longest side, i.e., the side opposite the right angle.
The Pythagorean Theorem • For a right triangle with legs a and b and hypotenuse c, a2+b2=c2.
Triangle Quiz • Please complete the following quiz that covers the information that was just presented to you.
If a triangle has three unequal sides it is a ______ triangle. A) Scalene B) Obtuse C) Isosceles Answer: A) Scalene Question 1
A triangle which has three equal angles is a ______ triangle. A) Acute B) Equilateral C) Equiangular Answer: C) Equiangular Question 2
A triangle with (at least) two equal sides is a ______ triangle. A) Scalene B) Isosceles C) Congruent Answer: B) Isosceles Question 3
Two triangles that are equal are called ______ triangles A) Acute B) Obtuse C) Congruent Answer: C) Congruent Question 4
A triangle with all three sides of equal length is a ______ triangle. A) Equilateral B) Right C) Equiangular Answer: A) Equilateral Question 5
A triangle with an angle of 90° is a ______ triangle. A) Acute B) Right C) Congruent Answer: B) Right Question 6
A triangle in which all three angles are less than 90° is a ______ triangle. A) Right B) Acute C) Scalene Answer: B) Acute Question 7
A triangle in which one of the angles is greater than 90° is a ______ triangle. A) Obtuse B) Isosceles C) Acute Answer: A) Obtuse Question 8
What is the Hypotenuse of a right triangle? A) The smallest angle. B) The side opposite the right angle. C) The right angle. Answer: B) The side opposite the right angle. Question 9
The Pythagorean Theorem states … A) pr2 B) (a+b)2/2=c C) a2+b2=c2 Answer: C) a2+b2=c2 Question 10
Use the Pythagorean Theorem to solve the following: a = 5 b = 12 c = ? Answer: c = 13 Question 11
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