(a) Copy and complete the table of values for the relation y = 3 sin

MATHEMATICS
WAEC 2020

(a) Copy and complete the table of values for the relation y = 3 sin 2x.

xo\(^o\)15\(^o\)30\(^o\)45\(^o\)60\(^o\)75\(^o\)90\(^o\)105\(^o\)120\(^o\)135\(^o\)

\(^o\)

y0.01.5-2.6

(b) Using a scale of 2 cm to 15° on the x-axis and 2cm to I unit on the y-axis, draw the graph of y = 3 sin 2x for 0° \(\geq\) x \(\geq\) 150°.

(c) Use the graph to find the truth set of;

(i) 3 sin 2x + 2 = 0;

(ii ) \(\frac{3}{2}\) sin 2x = 0.25.

Explanation

xo\(^o\)15\(^o\)30\(^o\)45\(^o\)60\(^o\)75\(^o\)90\(^o\)105\(^o\)120\(^o\)135\(^o\)

\(^o\)

y0.01.52.62.12.61.50- 1.5- 2.6- 3-2.6

y = 35m\(^2\)x

when x = 15\(^o\)

y = 3 sin = (15\(^o\))

y = sin 30\(^o\)

y = 3 x \(\frac{1}{2}\) = 1.5

When x = 30\(^o\)

y = 3 sin 2(30\(^o\))

y = 3 sin 60\(^o\) = 2.6

When x = 45\(^o\)

y = 3sin45\(^o\)

= 2.1

When x = 60\(^o\)

y = 3 sin 2(60\(^o\))

= 2 sin 120\(^o\)

= 2.6

When x = 75\(^o\)

y = 3 sin 2(75\(^o\))

= 3 sin 150\(^o\)

= 1.5

When x = 90\(^o\)

y = 3 sin 2(90\(^o\))

= 3 sin 180\(^o\)

= 0

When x = 105\(^o\)

y = 3 sin 2(105\(^o\))

= sin 210\(^o\)

= -1.5

When x = 120\(^o\)

y = 3 sin 2(120\(^o\))

= 3 sin 240\(^o\)

= -2.6

When x = 135\(^o\)

y = 3 sin 2(135\(^o\))

y = 3 sin 270\(^o\)

y = -3

(b

(c)(i) 113

(ii) 3\(^o\) and 82\(^o\)



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