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Example Questions
Example Question #11 : Isosceles Triangles
An isoceles triangle has a base angle that is
degrees less than three times the vertex angle. What is the product of the vertex angle and the base angle?
Every triangle has 180 degrees. An isoceles triangle has one vertex angle and two congruent base angles.
Let
vertex angle and base angle.Then the equation to solve becomes:
, or .
Then the vertex angle is
, the base angle is , and the product is .
Example Question #224 : Geometry
In triangle ABC, Angle A = x degrees, Angle B = 2x degrees, and Angle C = 3x+30 degrees. How many degrees is Angle B?
45°
25°
50°
30°
105°
50°
Because the interior angles of a triangle add up to 180°, we can create an equation using the variables given in the problem: x+2x+(3x+30)=180. This simplifies to 6X+30=180. When we subtract 30 from both sides, we get 6x=150. Then, when we divide both sides by 6, we get x=25. Because Angle B=2x degrees, we multiply 25 times 2. Thus, Angle B is equal to 50°. If you got an answer of 25, you may have forgotten to multiply by 2. If you got 105, you may have found Angle C instead of Angle B.
Example Question #221 : Geometry
An isosceles triangle has a base angle that is six more than three times 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
= vertex angle and = base angle.Then the equation to solve becomes
or
.
Solving for
gives a vertex angle of 24 degrees and a base angle of 78 degrees.Example Question #2 : How To Find An Angle In An Acute / Obtuse Isosceles Triangle
The base angle of an isosceles triangle is thirteen more than three times the vertex angle. What is the difference between the vertex angle and the base angle?
Every triangle has
. An isosceles triangle has one vertex ange, and two congruent base angles.Let
be the vertex angle and be the base angle.The equation to solve becomes
, since the base angle occurs twice.
Now we can solve for the vertex angle.
The difference between the vertex angle and the base angle is
.Example Question #11 : How To Find An Angle In An Acute / Obtuse Isosceles Triangle
An isoceles triangle has a base angle that is five less than twice the vertex angle. What is the sum of the base and vertex angles?
Each triangle has
degrees.An isoceles triangle has two congruent base angles and one vertex angle.
Let
vertex angle and base angle.Then the equation to solve becomes
or .Add
to both sides to get .Divide both sides by
to get vertex angle and base angles, so the sum of the angles is .Example Question #281 : Plane Geometry
An isoceles triangle has a base angle that is twice the vertex angle. What is the sum of one base angle and the vertex angle?
Every triangle contains
degrees. An isoceles triangle has two congruent base angles and one vertex angle.Let
the vertex angle and the base angleSo the equation to solve becomes
or and dividing by gives for the vertex angle and for the base angle, so the sum isAll High School Math Resources
