What is the value of cos((9pi)/6) ?

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cos((9pi)/6)

cos (\frac{9 π}{6})

0

Solution steps

cos (\frac{9 π}{6})

Simplify:

\frac{9 π}{6} = \frac{3 π}{2}

= cos (\frac{3 π}{2})

Rewrite using trig identities:

cos (π) cos (\frac{π}{2}) - sin (π) sin (\frac{π}{2})

= cos (π) cos (\frac{π}{2}) - sin (π) sin (\frac{π}{2})

Use the following trivial identity:

cos (π) = (- 1)

Use the following trivial identity:

cos (\frac{π}{2}) = 0

Use the following trivial identity:

sin (π) = 0

Use the following trivial identity:

sin (\frac{π}{2}) = 1

= (- 1) \cdot 0 - 0 \cdot 1

Simplify

= 0

arctan (tan (- \frac{3 π}{5}))

arccos (\frac{52}{56})

cos (3 (\frac{π}{4}))

arctan (\frac{60}{30})

400 \cdot cos (6 0^{\circ})