JAMB Mathematics Past Questions & Answers - Page 302

1,506.

Evaluate ∫\(^{\pi}_{2}\)(sec2 x - tan2x)dx

A.

\(\frac{\pi}{2}\)

B.

\(\pi\) - 2

C.

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

D.

\(\pi\) + 2

Correct answer is B

∫\(^{\pi}_{2}\)(sec2 x - tan2x)dx

∫\(^{\pi}_{2}\) dx = [X]\(^{\pi}_{2}\)

= \(\pi\) - 2 + c

when c is an arbitrary constant of integration

1,507.

Differentiate \(\frac{x}{cosx}\) with respect to x

A.

1 + x sec x tan x

B.

1 + sec2 x

C.

cos x + x tan x

D.

x sec x tan x + secx

Correct answer is D

let y = \(\frac{x}{cosx}\) = x sec x

y = u(x) v (x0

\(\frac{dy}{dx}\) = U\(\frac{dy}{dx}\) + V\(\frac{du}{dx}\)

dy x [secx tanx] + secx

x = x secx tanx + secx

1,508.

If y = 243(4x + 5)-2, find \(\frac{dy}{dx}\) when x = 1

A.

\(\frac{-8}{3}\)

B.

\(\frac{3}{8}\)

C.

\(\frac{9}{8}\)

D.

-\(\frac{8}{9}\)

Correct answer is A

y = 243(4x + 5)-2, find \(\frac{dy}{dx}\)

= -1944(4x + 5)-3

= 1944(9)-3

\(\frac{dy}{dx}\) when x = 1

= -\(\frac{1944}{9^3}\)

= -\(\frac{1944}{729}\)

= \(\frac{-8}{3}\)

1,509.

From the top of a vertical mast 150m high., two huts on the same ground level are observed. One due east and the other due west of the mast. Their angles of depression are 60° and 45° respectively. Find the distance between the huts

A.

150(1 + \(\sqrt{3}\))m

B.

50( \(\sqrt{3}\) - \(\sqrt{3}\))m

C.

150 \(\sqrt{3}\)m

D.

\(\frac{50}{\sqrt{3}}\)m

Correct answer is B

\(\frac{150}{Z}\) = tan 60o,

Z = \(\frac{150}{tan 60^o}\)

= \(\frac{150}{3}\)

= 50\(\sqrt{3}\)cm

\(\frac{150}{X x Z}\) = tan45o = 1

X + Z = 150

X = 150 - Z

= 150 - 50\(\sqrt{3}\)

= 50( \(\sqrt{3}\) - \(\sqrt{3}\))m

1,510.

solve the equation cos x + sin x \(\frac{1}{cos x - sinx}\) for values of such that 0 \(\leq\) x < 2\(\pi\)

A.

\(\frac{\pi}{2}\), \(\frac{3\pi}{2}\)

B.

\(\frac{\pi}{3}\), \(\frac{2\pi}{3}\)

C.

0, \(\frac{\pi}{3}\)

D.

0, \(\pi\)

Correct answer is D

cos x + sin x \(\frac{1}{cos x - sinx}\)

= (cosx + sinx)(cosx - sinx) = 1

= cos2x + sin2x = 1

cos2x - (1 - cos2x) = 1

= 2cos2x = 2

cos2x = 1

= cosx = \(\pm\)1 = x

= cos-1x (\(\pm\), 1)

= 0, \(\pi\) \(\frac{3}{2}\pi\), 2\(\pi\)

(possible solution)