Write the following theorems.
1) Vertically opposite angles theorem
2) Interior angles theorem
3) Theorem of remote interior angles of a triangle
Answers
Answer:
Vertical Angles: Theorem and Proof
Theorem: In a pair of intersecting lines the vertically opposite angles are equal.
Proof: Consider two lines AB←→ and CD←→ which intersect each other at O. The two pairs of vertical angles are:
i) ∠AOD and ∠COB
ii) ∠AOC and ∠BOD
Vertically opposite angles
It can be seen that ray OA¯¯¯¯¯¯¯¯ stands on the line CD←→ and according to Linear Pair Axiom, if a ray stands on a line, then the adjacent angles form a linear pair of angles.
Therefore, ∠AOD + ∠AOC = 180° —(1) (Linear pair of angles)
Similarly, OC¯¯¯¯¯¯¯¯ stands on the line AB←→.
Therefore, ∠AOC + ∠BOC = 180° —(2) (Linear pair of angles)
From (1) and (2),
∠AOD + ∠AOC = ∠AOC + ∠BOC
⇒ ∠AOD = ∠BOC —(3)
Also, OD¯¯¯¯¯¯¯¯ stands on the line AB←→.
Therefore, ∠AOD + ∠BOD = 180° —(4) (Linear pair of angles)
From (1) and (4),
∠AOD + ∠AOC = ∠AOD + ∠BOD
⇒ ∠AOC = ∠BOD —(5)
Thus, the pair of opposite angles are equal.
Ans 2
The alternate interior angles theorem states that, the alternate interior angles are congruent when the transversal intersects two parallel lines. Hence, it is proved. Alternate interior angles can be calculated by using properties of the parallel lines.
Ans 3
If we extend any of the sides of a triangle, it will form an outside or exterior angle with the triangle. Remote interior angles are angles that don't share a vertex or corner of a triangle with the exterior angle. The measure of the exterior angle equals the sum of the two remote interior angles.
Answer:
Step-by-step explanation:
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