# Main/central vertex

ABC is an isosceles triangle with base BC and main vertex A. The angle at vertex A is 18°. What will be the size of the angle at vertex B?

B =  81 °

### Step-by-step explanation:

We will be pleased if You send us any improvements to this math problem. Thank you!

Tips to related online calculators

#### You need to know the following knowledge to solve this word math problem:

We encourage you to watch this tutorial video on this math problem:

## Related math problems and questions:

The size of two internal angles of a triangle ABC are α=6/18π and β=7/18π. Calculate the size of the third angle.
• Angles
The outer angle of the triangle ABC at the vertex A is 114°12'. The outer angle at the vertex B is 139°18'. What size is the internal angle at the vertex C?
• Outer angles
The outer angle of the triangle ABC at the A vertex is 71°40 ' outer angle at the vertex B is 136°50'. What size has the inner triangle angle at the vertex C?
• Inner angles
The magnitude of the internal angle at the main vertex C of the isosceles triangle ABC is 72°. The line p, parallel to the base of this triangle, divides the triangle into a trapezoid and a smaller triangle. How big are the inner angles of the trapezoid?
• Gamma angle
Find the magnitude of the gamma angle in triangle ABC if: α = 38° 56 ’and β = 47° 54’.
• Isosceles - isosceles
It is given a triangle ABC with sides /AB/ = 3 cm /BC/ = 10 cm, and the angle ABC = 120°. Draw all points X such that true that BCX triangle is an isosceles and triangle ABX is isosceles with the base AB.
• MO Z7–I–6 2021
In the triangle ABC, point D lies on the AC side and point E on the BC side. The sizes of the angles ABD, BAE, CAE and CBD are 30°, 60°, 20° and 30°, respectively. Find the size of the AED angle.
• Draw triangle
Construct an isosceles triangle ABC, if AB = 7cm, the size of the angle ABC is 47°, arms | AC | = | BC |. Measure the size of the BC side in mm.
• Central angle
What is the length of the arc of a circle with a diameter of 46 cm, which belongs to a central angle of 30°?
• Find the
Find the third interior angle of the triangle ABC where: α = 48°, γ = 65°.
• The central
The central angle of a sector is 30° and the radius is 15 m. Determine its perimeter.
• Isosceles triangle
The circumference of the isosceles triangle is 32.5 dm. Base length is 153 cm. How long is the leg of this triangle?
• Isosceles trapezium
Trapezoid YUEB (YU||EB) is isosceles. The size of the angle at vertex U is 49 degrees. Calculate the size of the angle at vertex B.
• Triangles
Equilateral triangle with side 40 cm has the same perimeter as an isosceles triangle with arm of 45 cm. Calculate the base x of an isosceles triangle.
• Isosceles triangle
In an isosceles triangle ABC with base AB; A [3,4]; B [1,6] and the vertex C lies on the line 5x - 6y - 16 = 0. Calculate the coordinates of vertex C.
• Isosceles
Isosceles trapezium ABCD ABC = 12 angle ABC = 40 ° b=6. Calculate the circumference and area.
• Elevation angles
From the endpoints of the base 240 m long and inclined at an angle of 18° 15 ', the top of the mountain can be seen at elevation angles of 43° and 51°. How high is the mountain?