Answer:
[tex]x = 145[/tex]
Step-by-step explanation:
1.Approach
To find the value of (x), one will have to take multiple steps. Since a straight line is (180) degrees, one can use this property. Subtract the measure of the exterior angle (the angle formed between the extension of the side of a triangle, and the side of a triangle) from (180) to find an expression to describe the measure of the angle inside the triangle.
Then one is given a regular octagon, using the sum of interior angles formula, find the measure of any interior angle. The vertical angles that when two lines intersect, the opposite angles are congruent. One can use this property to find the final unknown angle in the triangle.
It is known that the sum of angles in a triangle is (180). Use this to find the measure of (x).
2. Find the measure of two angles in the triangle
The degree measure of a straight angle is (180), therefore, when two angles form a straight line, their sum of (180). One can apply this here by stating,
[tex]x+(unknown)=180[/tex]
Solve for unknown,
[tex]unknown = 180 - x[/tex]
One can also state,
[tex]170+(unknown_2)=180[/tex]
Solve for the unknown,
[tex]unknown_2=10[/tex]
3.Find the degree measure of one of the angles in the octagon
The given octagon (eight-sided figure) is a regular octagon. By its definition, all of the sides in any regular polygon are congruent. This is indicated here, thus the octagon is a regular octagon. One property of a regular polygon is that all of the angles in the figure are cognrunet. This means that the sum of interior angles divided by the number of angles wil give one the measurement of each angle.
The formula to find the sum of interior angles in a polygon is as follows,
[tex]S=180(n-2)[/tex]
Where (n) is the number of sides. Since an octagon has (8) sides substitute this number into the formula and solve for the sum of angles,
[tex]S=180(n-2)\\\\S=180(8-2)[/tex]
Simplify,
[tex]S=180(8-2)\\\\S=180(6)\\\\S= 1080[/tex]
Now divide by the number of angles. The number of angles in an octagon is (8). Since this is a regular octagon, all of the angles are congruent, thus dividing the sum of angles by the number of angles will give on the measure of each angle.
[tex]1080[/tex] ÷ [tex]8 = 135[/tex]
4. Find the measure of the final angle in the triangle
The vertical angles theorem states that when two lines intersect, the angles opposite each other are congruent. Therefore, the final unknown angle in this triangle is equal to (135) degrees, because the angle opposite in the octagon is equal to (135) degrees.
5. Find the meausre of (x)
The sum of angles in any triangle is (180) degrees. Since one has found the measure or expression of the angle measure of each angle in a triangle, one can form an equation and solve for the unknown,
[tex](180-x)+(10)+(135)=180[/tex]
Simplify,
[tex]325-x=180[/tex]
Inverse operations,
[tex]325-x=180\\\\-x = -145\\\\x=145[/tex]
