WAEC Further Mathematics Past Questions & Answers - Page 88

436.

Find the remainder when \(5x^{3} + 2x^{2} - 7x - 5\) is divided by (x - 2).

A.

-51

B.

-23

C.

29

D.

49

Correct answer is C

Using remainder theorem, the remainder when \(5x^{3} + 2x^{2} - 7x -5\) is divided by (x - 2) = f(2)

\(f(2) = 5(2^{3}) + 2(2^{2}) - 7(2) -5 = 40 + 8 - 14 - 5\)

= 29

437.

Evaluate \(\cos (\frac{\pi}{2} + \frac{\pi}{3})\)

A.

\(\frac{-2}{\sqrt{3}}\)

B.

\(\frac{-\sqrt{3}}{2}\)

C.

\(\frac{\sqrt{3}}{4}\)

D.

\(\frac{4}{\sqrt{3}}\)

Correct answer is B

\(\cos (x + y) = \cos x \cos y - \sin x \sin y\)

\(\cos (\frac{\pi}{2} + \frac{\pi}{3}) = \cos \frac{\pi}{2} \cos \frac{\pi}{3} - \sin \frac{\pi}{2} \sin \frac{\pi}{3}\)

= \((0 \times \frac{1}{2}) - (1 \times \frac{\sqrt{3}}{2})\)

= \(0 - \frac{\sqrt{3}}{2} = -\frac{\sqrt{3}}{2}\)

438.

If \(\log_{9} 3 + 2x = 1\), find x.

A.

\(\frac{-1}{2}\)

B.

\(\frac{-1}{4}\)

C.

\(\frac{1}{4}\)

D.

\(\frac{1}{2}\)

Correct answer is C

\(\log_{9} 3 = \log_{9} (9^{\frac{1}{2}}) = \frac{1}{2}\log_{9} 9 = \frac{1}{2}\)

\(\frac{1}{2} + 2x = 1 \implies 2x = \frac{1}{2}\)

\(x = \frac{1}{4}\)

439.

Express 75° in radians, leaving your answer in terms of \(\pi\).

A.

\(\frac{5\pi}{12}\)

B.

\(\frac{3\pi}{4}\)

C.

\(\frac{5\pi}{6}\)

D.

\(\frac{7\pi}{6}\)

Correct answer is A

\(180° = \pi rads\)

\(1° = \frac{\pi}{180}\)

\(\therefore 75° = \frac{\pi}{180} \times 75 \)

= \(\frac{5\pi}{12}\)