Math Problem Statement

Find the value of the marked angles in each of the following diagrams: (a) angle at F is 23°, and (b) exterior angle at B is 98°.

Solution

Let’s solve both parts of Question 8 based on the image.

Part (a):

We need to find the value of angle xx. From the diagram:

  • Angle AFG=23\angle AFG = 23^\circ
  • Angle GFE\angle GFE is the angle we are looking for (denoted as xx).

From the diagram, we can see that AFG\angle AFG and GFE\angle GFE are on a straight line at point FF, meaning they are supplementary angles.

So, we use the property of supplementary angles: x+23=180x + 23^\circ = 180^\circ x=18023x = 180^\circ - 23^\circ x=157x = 157^\circ

Thus, for part (a), x=157x = 157^\circ.

Part (b):

In this part, we need to find xx, the exterior angle of a triangle ABCABC at point BB. We know:

  • ABC=98\angle ABC = 98^\circ (the exterior angle),
  • The two base angles ACB=BDC\angle ACB = \angle BDC, because they are opposite angles of an isosceles triangle.

For an isosceles triangle, the exterior angle is equal to the sum of the two interior opposite angles. So: Exterior angle x=ACB+BDC\text{Exterior angle } x = \angle ACB + \angle BDC Since both base angles are equal, let each base angle be yy. Then: x=2yx = 2y Also, we know that the exterior angle is supplementary to 9898^\circ, i.e., x+98=180x + 98^\circ = 180^\circ x=18098=82x = 180^\circ - 98^\circ = 82^\circ

Thus, for part (b), x=82x = 82^\circ.


If you'd like more details or have any questions, feel free to ask! Here are some related questions you might want to explore:

  1. What is the sum of angles in a triangle?
  2. What are supplementary angles?
  3. How can you determine angles in an isosceles triangle?
  4. What is the relationship between exterior and interior angles of a triangle?
  5. How can you calculate angles when lines are parallel?

Tip: Always check for supplementary and vertically opposite angles when solving for unknowns in geometry diagrams!

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Math Problem Analysis

Mathematical Concepts

Supplementary Angles
Exterior Angles
Isosceles Triangles

Formulas

x + 23° = 180° (for supplementary angles)
x + 98° = 180° (for exterior angle of a triangle)

Theorems

Supplementary Angle Theorem
Exterior Angle Theorem
Isosceles Triangle Theorem

Suitable Grade Level

Grades 8-10