All High School Math Resources
Example Questions
Example Question #1 : How To Find An Angle In An Acute / Obtuse Triangle
In a given triangle, the angles are in a ratio of 1:3:5. What size is the middle angle?
Since the sum of the angles of a triangle is , and given that the angles are in a ratio of 1:3:5, let the measure of the smallest angle be , then the following expression could be written:
If the smallest angle is 20 degrees, then given that the middle angle is in ratio of 1:3, the middle angle would be 3 times as large, or 60 degrees.
Example Question #431 : Psat Mathematics
Triangle ABC has angle measures as follows:
What is ?
79
19
44
57
90
57
The sum of the measures of the angles of a triangle is 180.
Thus we set up the equation
After combining like terms and cancelling, we have
Thus
Example Question #431 : Psat Mathematics
The base angle of an isosceles triangle is five more than twice the vertex angle. What is the base angle?
Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let = the vertex angle and = the base angle
So the equation to solve becomes
Thus the vertex angle is 34 and the base angles are 73.
Example Question #1 : How To Find An Angle In An Acute / Obtuse Triangle
The base angle of an isosceles triangle is 15 less than three times the vertex angle. What is the vertex angle?
Every triangle contains 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let = vertex angle and = base angle
So the equation to solve becomes .
Example Question #1 : How To Find An Angle In An Acute / Obtuse Triangle
The base angle of an isosceles triangle is ten less than twice the vertex angle. What is the vertex angle?
Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let = vertex angle and = base angle
So the equation to solve becomes
So the vertex angle is 40 and the base angles is 70
Example Question #141 : Triangles
The base angle of an isosceles triangle is 10 more than twice the vertex angle. What is the vertex angle?
Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let = the vertex angle and = the base angle
So the equation to solve becomes
The vertex angle is 32 degrees and the base angle is 74 degrees
Example Question #432 : Geometry
In an isosceles triangle, the vertex angle is 15 less than the base angle. What is the base angle?
Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let = base angle and = vertex angle
So the equation to solve becomes
Thus, 65 is the base angle and 50 is the vertex angle.
Example Question #11 : Isosceles Triangles
In an isosceles triangle the vertex angle is half the base angle. What is the vertex angle?
Every triangle has 180 degrees. An isosceles triangle has one vertex angle and two congruent base angles.
Let = base angle and = vertex angle
So the equation to solve becomes , thus is the base angle and is the vertex angle.
Example Question #1 : How To Find An Angle In An Acute / Obtuse Triangle
If the average of the measures of two angles in a triangle is 75o, what is the measure of the third angle in this triangle?
75°
40°
30°
65°
50°
30°
The sum of the angles in a triangle is 180o: a + b + c = 180
In this case, the average of a and b is 75:
(a + b)/2 = 75, then multiply both sides by 2
(a + b) = 150, then substitute into first equation
150 + c = 180
c = 30
Example Question #231 : Plane Geometry
Which of the following can NOT be the angles of a triangle?
45, 90, 100
30, 60, 90
1, 2, 177
30.5, 40.1, 109.4
45, 45, 90
45, 90, 100
In a triangle, there can only be one obtuse angle. Additionally, all the angle measures must add up to 180.