NCERT Class 9 MathematicsGeometry Board Sample Problems (For CBSE, ICSE, IAS, NET, NRA 2022)

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Types of angles

Table Supporting: NCERT Class 9 MathematicsGeometry Board Sample Problems
Acute Angle

Acute Angle
Obtuse Angle

Obtuse Angle
Right Angle

Right Angle
Reflex Angle

Reflex Angle
Straight Angle

Straight Angle

Complimentary Angles:

Two angles whose sum equal to

Complimentary Angles

Supplementary Angles

Two angles whose sum equal to

Supplementary Angles

Angles rules

Angles rules

Angles in a Triangle

Angles in a triangle add up to

So a + b + c =

Angles on a Straight Line

Angles on a straight line add Up to

Angles in a Quadrilateral

Angles in a quadrilateral add up to .

So

Angles Around a Point

Angles around a point add up to .

So

If the side of the triangle is produced, the exterior angle formed is equal to the sum of the opposite interior angle

Triangle is Produced

Vertically Opposite angles

If two lines intersect with each other, then vertically opposite angles are equal

Vertically Opposite Angles

Transversal across the parallel Lines

If the transversal intersect two parallel lines

Transversal Across the Parallel Lines

a) Each pair of corresponding angles are equals

b) Each pair of alternate interior angles are equal

c) Each pair of interior angles on the same side of the transversal is supplementary

If a transversal intersect two lines such that either

a) Any one pair of corresponding angles are equal

b) Any one pair of alternate interior angles are equal

c) Any one pair of interior angles on the same side of the transversal is supplementary

Then the two lines are parallel

Parallel lines Note

Lines which are parallel to a given line are parallel with each other