WAEC Mathematics Past Questions & Answers - Page 342

1,706.

If sin\( \theta \) = K find tan\(\theta\), 0° \(\leq\) \(\theta\) \(\leq\) 90°.

A.

1-K

B.

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

C.

\( \frac{k}{\sqrt{1 - k^2}} \)

D.

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

E.

\( \frac{k}{\sqrt{ k^2 - 1}} \)

Correct answer is C

\(\sin \theta = \frac{k}{1}\)

\(\implies 1^2 = k^2 + adj^2\)

\(adj = \sqrt{1 - k^2}\)

\(\therefore \tan \theta = \frac{k}{\sqrt{1 - k^2}}\)

1,707.

If the 2nd and 5th terms of a G.P are 6 and 48 respectively, find the sum of the first for term

A.

-45

B.

-15

C.

15

D.

33

E.

45

Correct answer is E

T\(_{2}\) = ar = 6

T\(_{5}\) = ar\(^{4}\) = 48

\(\frac{T_5}{T_2}\) = \(\frac{ar^{4}}{ar}\) = \(\frac{48}{6}\)

= r\(^{3}\) = 8

⇒ r = 2

S\(_{n}\) = \(\frac{a((r^n) - 1)}{r - 1}\)

S\(_{4}\) = \(\frac{a((r^4) - 1)}{r - 1}\)

S\(_{4}\) = \(\frac{3((2^4) - 1)}{2 - 1}\)

= 3(16 -1)

= 45