Math Problem Statement

Find the values of x, y, and z in the given figure where triangle ABC is isosceles with AB = AC, angle C = 70°, and external angle z formed by line CD.

Solution

The image shows a geometric problem where you are asked to find the values of xx, yy, and zz based on the figure. Here's the breakdown of the relevant elements from the figure and given information:

Information from the image:

  • The triangle is labeled ABC\triangle ABC, with additional points DD and EE outside the triangle.
  • C\angle C is marked as 7070^\circ, and the angle adjacent to C\angle C (on line CDCD) is labeled zz.
  • A\angle A is labeled xx.
  • B\angle B is labeled yy.
  • Line segments ABAB and ACAC are marked as equal (suggesting ABC\triangle ABC is isosceles with AB=ACAB = AC).

Steps to find the angles:

  1. Angle at CC:

    • Since C=70\angle C = 70^\circ, and the line CDCD continues straight, the exterior angle zz adjacent to CC can be found using the linear pair relationship: C+z=180\angle C + z = 180^\circ So, z=18070=110.z = 180^\circ - 70^\circ = 110^\circ.
  2. Isosceles Triangle Property:

    • Since ABC\triangle ABC is isosceles with AB=ACAB = AC, the angles opposite these sides are equal: A=B=x=y.\angle A = \angle B = x = y.
  3. Sum of Angles in a Triangle:

    • In any triangle, the sum of the interior angles is 180180^\circ. For ABC\triangle ABC: x+y+C=180.x + y + \angle C = 180^\circ. Substituting the values: x+x+70=180x + x + 70^\circ = 180^\circ 2x=110    x=55.2x = 110^\circ \implies x = 55^\circ. Therefore, y=x=55y = x = 55^\circ.

Final Answers:

  • x=55x = 55^\circ,
  • y=55y = 55^\circ,
  • z=110z = 110^\circ.

Let me know if you'd like further clarification or additional steps!

Here are some related questions to explore:

  1. How would the solution change if ABACAB \neq AC?
  2. What is the sum of exterior angles of any triangle?
  3. How can you prove the isosceles triangle property geometrically?
  4. What would zz be if C\angle C were 8080^\circ?
  5. Can you find an alternate method to calculate zz?

Tip: Always look for properties like equal sides or parallel lines in geometry to simplify angle calculations!

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Math Problem Analysis

Mathematical Concepts

Geometry
Isosceles Triangle
Angle Properties
Linear Pair

Formulas

Sum of angles in a triangle: x + y + angle C = 180°
Linear pair of angles: angle C + z = 180°

Theorems

Isosceles Triangle Theorem: In an isosceles triangle, the base angles are equal.
Linear Pair Theorem: Adjacent angles on a straight line sum to 180°.

Suitable Grade Level

Grades 8-10