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?

Correct result:

A =  54 °
B =  54 °
C =  126 °
D =  126 °


γ=72 α=β α+β+γ=180 α+α+γ=180  α=180γ2=180722=54 β=α=54=54  A=α=54=54
C+B=180 C=180B=18054=126
A+D=180  D=C=126=126

We would be pleased if you find an error in the word problem or inaccuracies and send it to us. Thank you!

Showing 0 comments:

Tips to related online calculators
See also our trigonometric triangle calculator.

We encourage you to watch this tutorial video on this math problem: video1

Related math problems and questions:

  • Outer angles
    triangle_1111_3 The outer angle of the triangle ABC at the A vertex is 71°40 ' outer angle at the vertx B is 136°50'. What size has the inner triangle angle at the vertex C?
  • Internal angles
    mo-klm The ABCD is an isosceles trapezoid, which holds: |AB| = 2 |BC| = 2 |CD| = 2 |DA|: On its side BC is a K point such that |BK| = 2 |KC|, on its side CD is the point L such that |CL| = 2 |LD|, and on its side DA the point M is such that | DM | = 2 |MA|. Dete
  • Angles
    angles_1 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?
  • Internal angles
    triangle_5 Find the internal angles of the triangle ABC if the angle at the vertex C is twice the angle at the B and the angle at the vertex B is 4 degrees smaller than the angle at the vertex A.
  • Angle at the apex
    iso_3 In an isosceles triangle, the angle at the apex is 30° greater than the angle at the base. How big are the internal angles?
  • Acute triangle
    triangle2 In the acute triangle KLM, V is the intersection of its heights and X is the heel of height to the side KL. The axis of the angle XVL is parallel to the side LM and the angle MKL is 70°. What size are the KLM and KML angles?
  • Isosceles
    rr_lichobeznik_1 Isosceles trapezium ABCD ABC = 12 angle ABC = 40 ° b=6. Calculate the circumference and area.
  • Triangles
    triangles_6 Find out whether given sizes of the angles can be interior angles of a triangle: a) 23°10',84°30',72°20' b) 90°,41°33',48°37' c) 14°51',90°,75°49' d) 58°58',59°59',60°3'
  • Trapezoid v3
    licho_3 The isosceles trapezoid has the angle at a firsst base 40 degrees less than the angle at second base. How large angles has this trapezoid ?
  • Isosceles trapezoid v3
    rovnobezky_uhly In an isosceles trapezoid ABCD is the size of the angle β = 81° Determine size of angles α, γ and δ.
  • Triangle angles
    triangle_4 In a triangle ABC the interior angle at the vertex C is twice as the internal angle at the point A. Outer angle at the point B measured 117 degrees. How big is the outer angle at the vertex A?
  • Internal angles
    angle_3 One internal angle of the triangle JAR is 25 degrees. The difference is the size of the two other is 15°. Identify the size of these angles.
  • Two angles
    rt_1_1 The triangles ABC and A'B'C 'are similar. In the ABC triangle, the two angles are 25° and 65°. Explain why in the triangle A'B'C 'is the sum of two angles of 90 degrees.
  • Area and two angles
    trig_1 Calculate the size of all sides and internal angles of a triangle ABC, if it is given by area S = 501.9; and two internal angles α = 15°28' and β = 45°.
  • Parallelogram
    rovnobeznik_1 Find the perimeter of the parallelogram, where base a = 8 cm, height v = 3 cm, and angle alpha = 35° is the magnitude of the angle at vertex A.
  • Angles of a triangle
    triangles_9 In the triangle ABC, the angle beta is 15° greater than the angle alpha. The remaining angle is 30° greater than the sum of the angles alpha and beta. Calculate the angles of a triangle.
  • Angles
    triangle The triangle is one outer angle 158°54' and one internal angle 148°. Calculate the other internal angles of a triangle.