Question on: JAMB Mathematics - 1990
If Cos (\theta) = (\frac{12}{13}). Find (\theta) + cos2(\theta)
A
\(\frac{169}{25}\)
B
\(\frac{25}{169}\)
C
\(\frac{169}{144}\)
D
\(\frac{144}{169}\)
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Correct Option: A
Cos (\theta) = (\frac{12}{13})
x2 + 122 = 132
x2 = 169- 144 = 25
x = 25
= 5
Hence, tan(\theta) = (\frac{5}{12}) and cos(\theta) = (\frac{12}{13})
If cos2(\theta) = 1 + (\frac{1}{tan^2\theta})
= 1 + (\frac{1}{\frac{(5)^2}{12}})
= 1 + (\frac{1}{\frac{25}{144}})
= 1 + (\frac{144}{25})
= (\frac{25 + 144}{25})
= (\frac{169}{25})
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