Page 135 - Math Smart - 7

In this chapter

Pupils should be able to:
• calculate the sum of
angles at a point, on
a straight line and in
a triangle, and prove
that vertically opposite
angles are equal; derive
and use the property
that the angle sum of
^ RECALL a quadrilateral is 360
degrees

XOKis a straight line. Find Ld.
Spotlight

Adjacent angles are
angles that have the
1 same vertex and share a
^d=180° -
common side.

.^shared
common side
I

Q shared vertex
Aim: Find the sum of angles on a straight line in each diagram.
We know Aa is adjacent
Q /AOC is a straight line. ^ AOD is a straight line.
to Zb since:
B • both angles share a
common vertex 0
• both angles share a
common side 08
• both angles lie on
opposite sides of the
common side 08.
a) Use your protractor to a) Use your protractor to
measure the size of angles measure the size of angles
oand b. a, band c. Angles are measured in
degrees. Remember to
Aa =
Zo =
write the degree symbol
Zb =
zc
=
b) What is the sum of angles
a and b? b) What is the sum of angles
a, b and c?
Conclusion
The sum of angles on a straight line is