Let us see some basics concepts of lines and angles in geometry.
In geometry, a line is always straight. There is no curve. Its has no limit and it has infinite length.
A ray is a part of a line that has one endpoint and goes on infinitely in only one direction.
A line is a part of a straight line. There is no curve. Its has two endpoints and it has a definite length.
When two lines meet at a right angle, the lines are said to be perpendicular to each other.
In a right-angled triangle, if sum of two angles is 90° then the two angles are called complementary angles.
∠POQ + ∠QOR= 90°
In a straight angle, if the sum of two angles is 180° then the two angles are called supplementary angles. Two right-angle always supplementary angles.
∠POR + ∠POQ = ∠POQ = 180°
Two angles are known as adjacent angles if they have a common vertex and common arm and lies on the same straight line.
∠POR and ∠POQ adjacent angle. ∠POR + ∠POQ = 180°
Vertically opposite angles
When two lines intersect, the angles formed opposite to each other at the point of intersection (vertex) are called vertically opposite angles. Two angles that are opposite at vertex are congruent.
∠A & ∠C are vertically opposite angles. Similarly, ∠B & ∠D are vertically opposite angles.
∠A = ∠C & ∠B = ∠D
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