I must give the exact value of cos(3pi) without using a calculator. How do I do that?

Question

fortytherapper · Answer

Referring to the unit circle is your best choice.

According to the unit circle, every half a pi, also known as $$\pi/2$$ is 90 degrees

Let's first find the position of cos(pi), where would that be?

Remember that cos = x, sin = y, and the radius of the unit circle = 1

lifeisadangerousgame · Answer

cos (pi) is 1?

lifeisadangerousgame · Answer

-1*

lifeisadangerousgame · Answer

Oh, then cos(3pi) is -1 as well then?

fortytherapper · Answer

Correct, -1

And correct again, because each pi is 180 degrees around, good job

lifeisadangerousgame · Answer

What's the point of putting cos and sin if you can find it without that?

fortytherapper · Answer

I think it's for the values between each 90 degrees. If we don't know the unit circle, it would be hard to know what cos(7pi/4) is

lifeisadangerousgame · Answer

Oh, okay. I'm going to try out the rest, thank you!

fortytherapper · Answer

Anytime, message me if you get stuck!