An angle is the union of two non-collinear rays with a common initial point.
l) An angle whose measure is 90° is a right angle.
2) An angle whose measure is less than 90° is called an acute angle.
3) An angle whose measure is more than 90° is called an obtuse angle.
4) An angle whose measure is l80° is called an straight angle.
5) An angle whose measure is more than l80° is called a reflex angle.
6) The sum of all the angles around a point is equal to 360°.
Complementary Angles: Two angles, the sum of whose measure is 90° are called complementary angles
Supplementary Angles: Two angles, the sum of whose measure is l80° are called supplementary angles Transversal: A line which intersects two or more lines at distinct points is called a transversal ofthe given line. Angles made by a transversal with
ln the above figure AB and CD are two lines and QR is the transversal. Corresponding angles: Two angles on the same side of` a transversal are known as the corresponding angles if` both lie either above two lines or below the two lines.
Ll = L5, L2= L6, L3= L7 and
Alternate Interior Angles: ln the above figure L3 and L5 and L4 and L6 are alternate interior angles and are equal.
i.e. L3 =L5 and L4= L6
l. What is the angle which equals one-fifih of` its supplement?
a) l5° b) 30°
c) 36° d) 75°
Let angle be tita,
The angle is one-fifth of`its
Supplement is 5 times of` the angle
Supplementary angle = 5tita
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