1.

Find the values of the following trigonometric ratios:cos \(\cfrac{19\pi}6\)

Answer»

Given cos \(\cfrac{19\pi}6\)

⇒  cos \(\cfrac{19\pi}6\) = cos 570°

⇒ 570° = (90° × 6 + 30°)

570° lies in third quadrant in which cosine function is negative.

∴ cos (570°) = cos (90° × 6 + 30°)

= -cos (30°)

\(-\cfrac{\sqrt3}2\)



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