If √5 cosx + √15sinx = 0, for 0° < x < 360°, find the values of x.
30° and 150°
150° and 210°
150° and 330°
210° and 330°
Correct answer is C
√5 cosx + √15sinx = 0;
√5 (cosx + √3sinx) = 0
cosx = -sinx√3; sinxcos = −1√3
tanx = −1√3; x = 150° or 330°
292
272
192
172
Correct answer is C
Using the sum of an AP, Sn = \fran2 [ 2a + (n - 1)d]
S3 = \fra32 [ 2a + (3 - 1)d]
18 = \fra32 [ 2a + 2d]
2a + 2d = 12
a = 4
2(4) + 2d = 18 --> 8 + 2d = 12
2d = 4; d = 2
a = 4: a + d
= 4 + 2 = 6
a + 2d = 4 + 2]2]
= 8
product of the terms = 4 * 6 * 8 = 192
If sin x = 1213 and sin y = 45, where x and y are acute angles, find cos (x + y)
4865
1315
−3365
−4865
Correct answer is C
From Pythagoras' theorem
when sin x = 1213, cos x = 513
Using cos (x + y) = cosx cosy - sinxsiny
513 * 35 - 1213 * 45
= −3365
If ( 1- 2x)4 = 1 + px + qx2 - 32x3 + 164, find the value of (q - p)
-32
-16
16
32
Correct answer is D
( 1- 2x)4 = 1 + px + qx2 - 32x3 + 164
compared with: 1 - 8x + 24x2 - 32x3 + 164
q = 24 and p = -8
(q - p) = 24 - [-8] = 32