# Geometry Lines And Angles And Parallel Lines (Pre, Angles And Parallel Lines (Pre

Ancient mathematicians introduced the concept of lines to represent straight objects which had negligible width and depth. Considered as a breadth less length by Euclid, lines form the basis of Euclidean geometry.

Đang xem: Geometry lines and angles

When two rays (part of a straight line) intersect each other in the same plane, they form an angle. The point of intersection is called a vertex.

In this article, we go over the basic properties, definitions, and types of lines and angles related to geometry. We’ll also look at a few examples for you to understand the properties of lines and angles in a better manner.

In the diagram given above, angle DFE and angle BFC are represented by X and Y respectively. If ∠AFC = 100° and ∠BFE = 45° then what is the value of Y-X?

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### Solution

Step 1: Given

∠DFE = X∠BFC = Y∠AFC = 100°∠BFE = 45°

Step 2: To find

The value of Y-X

Step 3: Approach and Working out

To find Y-X, we need to find Y and X first.

Measure of angle Y:

We are given ∠AFC = 100° and,∠AFC + ∠BFC = 180° as the sum of angles on the same side straight line is 180°100° + ∠BFC = 180°∠BFC = Y = 80°

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Measure of angle X:

We are given ∠BFE = 45° and,∠DFE + ∠BFE + ∠BFC = 180° as the sum of angles on the same side straight line is 180°.X + 45° +80° = 180°X = 55°

Hence, Y – X = 80° – 55° =25°.

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