Math Problem Statement

What is the measure of angle C given that the quadrilateral is inscribed in a circle and the angle measures are expressed as 130 - x, 4x + 35, 95 - 2x, and 7x - 20?

Solution

To determine the measure of angle CC in this problem, let's analyze it step by step.


Given Information:

  1. The quadrilateral ABCDABCD is inscribed in a circle (cyclic quadrilateral).

  2. In a cyclic quadrilateral, the opposite angles are supplementary, meaning: Angle A+Angle C=180andAngle B+Angle D=180.\text{Angle A} + \text{Angle C} = 180^\circ \quad \text{and} \quad \text{Angle B} + \text{Angle D} = 180^\circ.

  3. The angles are expressed as follows:

    • A=130x\angle A = 130 - x,
    • B=4x+35\angle B = 4x + 35,
    • C=952x\angle C = 95 - 2x,
    • D=7x20\angle D = 7x - 20.

We are tasked to find the measure of angle CC.


Step 1: Use the cyclic quadrilateral property

From the property of a cyclic quadrilateral: A+C=180.\angle A + \angle C = 180^\circ. Substitute the given expressions for A\angle A and C\angle C: (130x)+(952x)=180.(130 - x) + (95 - 2x) = 180.


Step 2: Solve for xx

Simplify the equation: 130x+952x=180.130 - x + 95 - 2x = 180. Combine like terms: 2253x=180.225 - 3x = 180. Subtract 225 from both sides: 3x=45.-3x = -45. Divide by 3-3: x=15.x = 15.


Step 3: Find the measure of C\angle C

The expression for C\angle C is: C=952x.\angle C = 95 - 2x. Substitute x=15x = 15: C=952(15).\angle C = 95 - 2(15). Simplify: C=9530=65.\angle C = 95 - 30 = 65^\circ.


Final Answer:

The measure of angle CC is 65°.

Correct option: C. 65°


Do you want a detailed explanation for any step? Let me know!

Related Questions:

  1. What are the measures of the other angles AA, BB, and DD?
  2. Why are opposite angles in a cyclic quadrilateral supplementary?
  3. How would the solution change if the quadrilateral were not cyclic?
  4. Can we verify the solution by solving for all angles using x=15x = 15?
  5. What is the significance of cyclic quadrilaterals in geometry?

Tip: Always remember that in a cyclic quadrilateral, opposite angles sum up to 180180^\circ. This property is essential for solving such problems!

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Math Problem Analysis

Mathematical Concepts

Geometry
Cyclic Quadrilaterals
Algebra

Formulas

Opposite angles in a cyclic quadrilateral: ∠A + ∠C = 180°
Supplementary angles property

Theorems

Cyclic Quadrilateral Theorem

Suitable Grade Level

Grades 9-11