WAEC Mathematics Past Questions & Answers - Page 291

1,451.

Given that tan x = 5/12, what is the value of sin x + cos x ?

A.

5/13

B.

7/13

C.

12/13

D.

17/13

E.

5/12

Correct answer is D

\(\tan x = \frac{opp}{adj} = \frac{5}{12}\)

\(Hyp^2 = opp^2 + adj^2\)

\(Hyp^2 = 5^2 + 12^2\)

= \(25 + 144 = 169\)

\(Hyp = \sqrt{169} = 13\)

\(\sin x = \frac{5}{13}; \cos x = \frac{12}{13}\)

\(\sin x + \cos x = \frac{5}{13} + \frac{12}{13}\)

= \(\frac{17}{13}\)

1,453.

If sin x = cos 50o, then x equals

A.

40o

B.

45o

C.

50o

D.

90o

E.

130o

Correct answer is A

No explanation has been provided for this answer.

1,454.

A plane flies 90km on a bearing 030° and then flies 150km due east. How far east of the starting point is the plane?

A.

120km

B.

165km

C.

195km

D.

(150 + 45√3)km

E.

240km

Correct answer is C

No explanation has been provided for this answer.

1,455.

State the fifth and seventh terms of the sequence \(-2, -3, -4\frac{1}{2}, ...\)

A.

\(-\frac{81}{8}, -\frac{729}{32}\)

B.

\(\frac{8}{81}, \frac{72}{39}\)

C.

\(\frac{27}{729}, \frac{718}{39}\)

D.

\(-\frac{27}{16}, -\frac{79}{81}\)

E.

\(-\frac{21}{8}, \frac{32}{618}\)

Correct answer is A

\(-2, -3, -4\frac{1}{2}, ...\)

This is a G.P with r = 1\(\frac{1}{2}\).

\(T_{n} = ar^{n - 1}\) (terms of a G.P)

\(T_{5} = (-2)(\frac{3}{2})^{5 - 1}\)

= \(-2 \times \frac{81}{16}\)

= \(-\frac{81}{8}\)

\(T_{7} = (-2)(\frac{3}{2})^{7 - 1}\)

= \(-2 \times \frac{729}{64}\)

= \(-\frac{729}{32}\)