Posted by **Bill** on Saturday, June 2, 2007 at 2:41pm.

Find the exact value of cos 300 degrees.

thanks guys

cos 300 = 1/2 = 0.500

how do you know? I am supposed to show my work.

You ought to know the rule on 30-60-90 triangles. If the hyp is 2, the shorter side is 1, and the longer side is sqrt3.

what does that have to do with cos300?

Cos(x) = Cos(-x) (1)

Cos(x + 360) = cos(x) (2)

Cos(300) = (using (2)) cos(-60) = (using (1)) cos(60) = using what Bobpursley wrote above 1/2

where did you get 60 from?

Bill, the sixty came from the addition formula above. 300 + 60 = 360

Bob, it says Cos(x + 360) .

Cos(x + 360) = Cos(x)

substitute x = y - 360:

Cos(y - 360 + 360) = Cos(y - 360) --->

Cos(y) = Cos(y - 360)

Substitute y = 300:

cos(300) = cos(-60)

Where did you get substitute x = y - 360 from? I'm sorry, I am so confused. Do you think you could give me the formula or whatever and then show me how to plug in the 300, or is that what you are doing now?

## Answer This Question

## Related Questions

- Algebra 2 - find the exact value of cos 300 degrees.
- math - Determine exact value of cos(cos^-1(19 pi)). is this the cos (a+b)= cos a...
- Algebra II - Multiple Choice (theta) means the symbol 0 with the dash in it. 1.)...
- Trig - What is the exact value of cos 40 degrees cos 50 degrees minus sin 40 ...
- Algebra II - 1) Find the exact value of cos 105 degrees by using a half-angle ...
- trig - 2sin(x)cos(x)+cos(x)=0 I'm looking for exact value solutions in [0, 3&#...
- Trig hep, please? Thank you! - 1. Find the exact value of sin(195(degrees)) 2. ...
- Studying for Pre Cal exam - Find the fourth roots of − 1/2 + (square root)...
- math - If sin(x) = /45 and cos(y) = 5/13 with both x and y terminating in ...
- Math - If sin(x) = /45 and cos(y) = 5/13 with both x and y terminating in ...

More Related Questions