If Cos theta frac 12 13 Find theta cos2 theta - JAMB Mathematics 1990 Question

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})