Notation for Geometry:

A = area, P = perimeter, C = circumference
V = volume, H = Height, hyp = Hypotenuse

ANGLES and PARALLELS


(a) Two straight lines which meet at a point form an angle between them.




(b) Theorems :

1. If AOB is a straight line, then




2. The sum of all the angle at a point, each being adjacent to the next, is 4 right angles.





⇒ a + b + c + d + e = 360° (Angles at a point)

3. If two straight lines intersect, the vertically opposite angles are equal.




a = b, c = d (Vertically Opposite angles)


4. Parallel lines PQ and RS are cut by a transversal LM, then we have :





The corresponding angles are equal c = b (Corresponding angles, PQ || RS)
The alternate angles are equal a = b (Alternate angles, PQ || RS)
The interior angles are supplementary b + d = 2 right angles (Interior angles, PQ || RS)


5. (i) Two angles whose sum is 90°, are complementary. Each one is the complement of the other.
(ii) Two angles whose sum is 180º, are supplementary. Each one is the supplement of the other.