Page 283 - ICSE Math 7

LINES AND ANGLES

Lines and Angles

Parallel lines Complementary angles: two angles
with the sum of their measure is 90°

Intersecting lines Supplementary angles: two angles
with the sum of their measure is 180°

Perpendicular lines Adjacent angles: two angles lying on
the opposite sides of a common arm

Concurrent lines: and having the same vertex
lines which pass Vertically opposite angles: angles
through the same point
formed by two intersecting lines
Point of concurrence: without any common arm
common point of intersection
of two or more lines Linear pair: two supplementary
adjacent angles form a linear pair

Collinear points: points
which lie on the same plane

TRIANGLES

Triangle Classification of Triangles
Vertex

On the basis of sides On the basis of angles
Angle
Side Side
Interior Scalene triangle: all three Acute-angled triangle: measure
sides are different. of all angles is less than 90°.
Angle Angle
Vertex Vertex
Side
Isosceles triangle: any Obtuse-angled triangle: Measure
two sides are equal. of one angle greater than 90°.

Equilateral triangle: all Right-angled triangle: measure
three sides are equal. of one-angle equal to 90°.

Properties of Triangles

The sum of three angles of a triangle is 180°.

The exterior angle angle of a triangle is equal to the sum
of its two interior opposite angles.

In a right-angled triangle, the square of the hypotenuse is
equal to the sum of the squares of the other two sides.

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