Math Problem Statement

In the diagram, AD bisects ∠CAB, m∠ADB = 96° and m∠CAB = 64°. Find m∠C and explain how you know.

Solution

In this problem, we are asked to find the measure of angle C\angle C in triangle ABC\triangle ABC, given the following information:

  • AD\overline{AD} bisects CAB\angle CAB.
  • mADB=96m\angle ADB = 96^\circ.
  • mCAB=64m\angle CAB = 64^\circ.

Step-by-step solution:

  1. Angle Bisector Property: Since ADAD bisects CAB\angle CAB, it divides CAB\angle CAB into two equal angles. Therefore, mBAD=mCAD=mCAB2=642=32.m\angle BAD = m\angle CAD = \frac{m\angle CAB}{2} = \frac{64^\circ}{2} = 32^\circ.

  2. Sum of Angles in ADB\triangle ADB: We know that the sum of interior angles in any triangle is 180180^\circ. In triangle ADB\triangle ADB, the angles are BAD=32\angle BAD = 32^\circ, ADB=96\angle ADB = 96^\circ, and ABD\angle ABD. The sum of these angles must be: mBAD+mADB+mABD=180.m\angle BAD + m\angle ADB + m\angle ABD = 180^\circ. Substituting the known values: 32+96+mABD=180,32^\circ + 96^\circ + m\angle ABD = 180^\circ, mABD=180128=52.m\angle ABD = 180^\circ - 128^\circ = 52^\circ.

  3. Sum of Angles in ABC\triangle ABC: Now, let's consider the entire triangle ABC\triangle ABC. The sum of the interior angles in this triangle is also 180180^\circ. We know mCAB=64m\angle CAB = 64^\circ and mABC=52m\angle ABC = 52^\circ. Let mACB=mCm\angle ACB = m\angle C.

    The equation for the sum of the angles is: mCAB+mABC+mACB=180,m\angle CAB + m\angle ABC + m\angle ACB = 180^\circ, 64+52+mACB=180,64^\circ + 52^\circ + m\angle ACB = 180^\circ, mACB=180116=64.m\angle ACB = 180^\circ - 116^\circ = 64^\circ.

Final Answer:

The measure of C\angle C (or mACBm\angle ACB) is 6464^\circ.

Explanation:

We used the fact that the sum of angles in a triangle is always 180180^\circ, along with the information about angle bisectors and the given angles to solve for C\angle C.

Would you like more details on any part of this solution?

Here are some related questions for deeper understanding:

  1. What is the angle bisector theorem and how does it apply in this case?
  2. Why do the interior angles of a triangle always sum to 180180^\circ?
  3. Can this approach be used for all triangles, or only specific types?
  4. How would the problem change if AD\overline{AD} were not an angle bisector?
  5. How can we verify that ABC\triangle ABC is a scalene triangle based on the given angles?

Tip: Remember, angle bisectors create two equal angles by definition, and this is often key to solving geometric problems involving triangles!

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Math Problem Analysis

Mathematical Concepts

Geometry
Angle Bisector
Sum of Angles in a Triangle

Formulas

Sum of angles in a triangle: m∠A + m∠B + m∠C = 180°
Angle bisector property: bisects an angle into two equal parts

Theorems

Angle Bisector Theorem
Sum of Interior Angles of a Triangle

Suitable Grade Level

Grades 9-10