Answer
$\cos$ 30$^{\circ}$ = $\frac{\sqrt3}{2}$
Work Step by Step
$\cos$ 30$^{\circ}$
We must find side $x$ of the 30$^{\circ}$ - 60$^{\circ}$ Right Triangle.
Pythagorean Theorem: $c$$^{2}$ = $a$$^{2}$ + $b$$^{2}$
2$^{2}$ = 1$^{2}$ + $x$$^{2}$
4 = 1 + $x$$^{2}$
x$^{2}$ = 3
x = $\sqrt 3$
Now consider the triangle from the perspective of the 30$^{\circ}$ angle.
Hypotenuse = 2
Opposite = 1
Adjacent = $\sqrt 3$
$\cos$ 30$^{\circ}$ = $\frac{Adjacent}{Hypotenuse}$ = $\frac{1}{2}$
Therefore:
$\cos$ 30$^{\circ}$ = $\frac{\sqrt3}{2}$
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