Question

Find the cosine of 210. Round your answers to the nearest hundredth if necessary.

Answer 1

Consider

cos(210) = cos(180+30)

Remember that Cos (180+x) = +- cos(x)

Where the sign depends on the quadrant.
And 210 is on the Quandrant 3 so cos (210) must be negative.

Answer 2

opps and the sine sorry

Answer 3

would the sine be negative also?

Answer 4

Yes, in the Q3, both sine and cosine are negative.

Answer 5

How do I find them?

Answer 6

Well actually 30 is a famous angle whose trigonometric functions are known.

\[\sin(30) = \frac{ 1 }{ 2 }\]
\[\cos(30)=\frac{ \sqrt{3} }{ 2 }\]

Answer 7

-0.5,-0.87?

Answer 8

Correct.

sin(210) = -0.5
cos(210) = -0.87