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Find the value of a in the equation: cos (a + 14)° = sin (4a +...

Mathematics
WAEC 2023

Find the value of a in the equation: cos (a + 14)° = sin (4a + 6)°

  • A. 15
  • B. 17
  • C. 14
  • D. 21
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Correct Answer: Option C
Explanation

cos (a + 14)° = sin (4a + 6)°
Recall, cos θ = sin (90 - θ)
⇒ sin (90 - (a + 14)) = sin (4a + 6)
⇒ sin (90 - a - 14) = sin (4a + 6)
⇒ sin (76 - a) = sin (4a + 6)
⇒ 76 - a = 4a + 6
⇒ 76 - 6 = 4a + a
⇒ 70 = 5a

\(a = \frac{70}{5}\)

therefore, a = 14


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Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Join your school's WhatsApp group
NECO June/July 2024 - Get offline past questions & answers - Download objective & theory, all in one app 48789
Post-UTME Past Questions - Original materials are available here - Download PDF for your school of choice + 1 year SMS alerts
WAEC Past Questions, Objective & Theory, Study 100% offline, Download app now - 24709
Join your school's WhatsApp group