WAEC - Mathematics (2021 - No. 22)
if tanθ = \(frac{3}{4}\), 180° < θ < 270°, find the value of cosθ.
\(\frac{4}{5}\)
\(\frac{3}{5}\)
-\(\frac{4}{5}\)
-\(\frac{3}{5}\)
Explanation
tanθ = \(frac{3}{4}\) → tanθ = 0.75
θ = tan\(^{-1}\)[0.75] → 36.8698°
cosθ = cos[36.8698°]
→ 0.800 or \(frac{4}{5}\)
However; in the third quadrant Cosine is negative
i.e -\(frac{4}{5}\)
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