WAEC Further Mathematics Past Questions & Answers - Page 104

516.

If \(f(x) = x^{2}\)  and \(g(x) = \sin x\), find g o f.

A.

\(\sin^{2} x\)

B.

\(\sin x^{2}\)

C.

\((\sin x)x^{2}\)

D.

\(x \sin x\)

Correct answer is B

\(f(x) = x^{2}, g(x) = \sin x\)

\(g \circ f = g(x^{2}) = \sin x^{2}\)

517.

Express \(\log \frac{1}{8} + \log \frac{1}{2}\) in terms of \(\log 2\)

A.

3 log 2

B.

4 log 2

C.

-3 log 2

D.

-4 log 2

Correct answer is D

\(\log \frac{1}{8} + \log \frac{1}{2} = \log 8^{-1} + \log 2^{-1}\)

= \(\log 2^{-3} + \log 2^{-1}\)

= \(-3 \log 2 - 1 \log 2 = -4 \log 2\)

518.

Given that \(a^{\frac{5}{6}} \times a^{\frac{-1}{n}} = 1\), solve for n

A.

-6.00

B.

-1.20

C.

0.83

D.

1.20

Correct answer is D

\(a^{\frac{5}{6}} \times a^{\frac{-1}{n}} = 1\)

\(\implies a^{\frac{5}{6} + \frac{-1}{n}} = a^{0}\)

Equating bases, we have

\(\frac{5}{6} - \frac{1}{n} = 0\)

\(\frac{5n - 6}{6n} = 0\)

\(5n - 6 = 0 \implies 5n = 6\)

\(n = \frac{6}{5} = 1.20\)

519.

Solve: \(\sin \theta = \tan \theta\)

A.

200°

B.

90°

C.

60°

D.

Correct answer is D

\(\sin \theta = \tan \theta \implies \frac{\sin \theta}{1} = \frac{\sin \theta}{\cos \theta}\)

Equating, we have

\(\cos \theta = 1 \implies \theta = \cos^{-1} 1\)

= \(0°\)

520.

A binary operation * is defined on the set of real numbers, R, by \(x * y = x + y - xy\). If the identity element under the operation * is 0, find the inverse of \(x \in R\).

A.

\(\frac{-x}{1 - x}, x \neq 1\)

B.

\(\frac{1}{1 - x}, x \neq 1\)

C.

\(\frac{-1}{1 - x}, x \neq 1\)

D.

\(\frac{x}{1 - x}, x \neq 1\)

Correct answer is A

\(x * y = x + y - xy\)

Let \(x^{-1}\) be the inverse of x, so that

\(x * x^{-1} = x + x^{-1} - x(x^{-1}) = 0\)

\(x + x^{-1} - x(x^{-1}) = 0 \implies x(x^{-1}) - x^{-1} = x\)

\(x^{-1}(x - 1) = x \implies x^{-1} = \frac{x}{x - 1}\)

= \(\frac{x}{-(1 - x)} = \frac{-x}{1 - x}, x \neq 1\)