Question on: WAEC Mathematics - 2004
Given that sin (5x - 28)o = cos (3x - 50)o,0 < x < 90o, find the value of x
A
14o
B
21o
C
32o
D
39o
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Correct Option: B
Sin (5x β 28)o = cos (3x - 50)o
Since by the trigonometry relation
Sin(5x β 28)o = cos[90 β (5x β 28)]o
Hence cos(3x β 50)o = cos[90 β (5x β 28)]o
3x β 50 = 90 - (5x-28)
3x β 50 = 90 β 5x + 28
3x + 5x = 90 + 28 + 50
8x = 168
\(x = \frac{168}{8}=21^{\circ}\)
Since by the trigonometry relation
Sin(5x β 28)o = cos[90 β (5x β 28)]o
Hence cos(3x β 50)o = cos[90 β (5x β 28)]o
3x β 50 = 90 - (5x-28)
3x β 50 = 90 β 5x + 28
3x + 5x = 90 + 28 + 50
8x = 168
\(x = \frac{168}{8}=21^{\circ}\)
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