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WAEC Mathematics 2011 Paper

Question : 13

Total: 47

Solution:

Concept:

Angles that are combinations of

90^\circ

60^\circ

, and their bisections can be constructed with a ruler and compasses.

Explanation:

Construct a perpendicular line to obtain a

90^\circ

angle.

Bisect a

90^\circ

angle to obtain a

45^\circ

angle.

Place the

45^\circ

angle next to the

90^\circ

angle.

Their sum is:

90^\circ + 45^\circ = 135^\circ

So,

135^\circ

is constructible.

The angles

115^\circ

125^\circ

, and

145^\circ

cannot be formed by such simple constructions.

Answer:

135^\circ

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