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WAEC Further Mathematics 2020 Paper

Question : 3

Total: 39

^o

^o

Solution:

Concept:

When

\cos x

is negative,

x

lies in the second quadrant or third quadrant.

Explanation:

First find the reference angle using the positive value:

\cos^{-1}(0.7133) = 44.5^\circ

Since

\cos x = -0.7133

, the required angles are:

In the second quadrant:

x = 180^\circ - 44.5^\circ = 135.5^\circ

In the third quadrant:

x = 180^\circ + 44.5^\circ = 224.5^\circ

Thus the values of

x

are

135.5^\circ

and

224.5^\circ

Answer:

135.5^\circ

224.5^\circ

Option D.

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