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

**Geometry Lines And Angles And Parallel Lines (Pre, Angles And Parallel Lines (Pre**in

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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.

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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?

2025303540

### 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.

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*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°

*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°.

**Geometry**