Isosceles Triangles

Isosceles Triangles

by Mitchell Stanberry

Multiple Choice

Which would be the best classification for the triangle shown?

• acute isosceles
• right scalene
• acute scalene
• obtuse scalene

Multiple Choice

Which would be the best classification for the triangle shown?

• right isosceles
• obtuse scalene
• obtuse isosceles
• right scalene

Multiple Choice

Which would be the best classification for the triangle shown?

• acute isosceles
• equiangular scalene
• equiangular isosceles
• equiangular equilateral

Isosceles Triangle Theorem

If two sides of a triangle are congruent, then the angles opposite those sides (the base angles) are congruent.

Converse of the Isosceles Triangle Theorem

If two angles of a triangle are congruent, then the sides opposite those angles are congruent.

Multiple Choice

Which pair of angles is congruent?

• <A and <B

• <A and <C

• <B and <C

• none of them

Multiple Choice

Which pair of sides is congruent?

• AC and BC

• AC and AB

• AB and BC

• none of them

m<1=_______

How do we go about solving for <1?

Fill in the Blank

m<1=?

x=?

How do we determine the length of a missing side?

x=12

• Determine which sides are congruent.

• Set the congruent sides equal to each other and solve.

Multiple Choice

Which equation would you use to determine what x is?

• $$7x-10=15x-35$$

• $$15x-35=3x+6$$

• $$7x-10=3x+6$$

Fill in the Blank

$$\overline{GK}=$$  

Multiple Choice

The Triangle Sum Theorem states that the sum of all angles in a triangle is ______. 

• 45°
• 90°
• 180°
• 360°

Multiple Choice

What is the value of the missing angle?

• 61
• 50
• 60
• 69

Multiple Choice

What is the value of x?

• 10
• 5
• -12
• 9

Multiple Choice

What is the value of the < A

• 151

• 68

• 80

• 78

Multiple Choice

Which angle is the vertex angle?

• <C
• <A
• <B

Multiple Choice

Find x.

• 180
• 57
• 61.5
• 32.7

Multiple Choice

Find the measure of the indicated angle. 

• 145 degrees
• 24 degrees
• 20 degrees 
• 21 degrees

Multiple Choice

Find x

• 90
• 45
• 22
• 35

Multiple Choice

Find the value of x.

• 1

• 4

• 5

• 8

Multiple Choice

Find x

• 60
• 48
• 30
• 28

Multiple Choice

Solve for x.

• 7
• 9
• 10
• -11