SOLUTION: Cos(-540 degrees) - tan 405 degrees. I converted the degrees into radians to find the exact spots on the unit circle. I get 1/2 as the answer, but not sure if I'm doing it right

Algebra ->  Test -> SOLUTION: Cos(-540 degrees) - tan 405 degrees. I converted the degrees into radians to find the exact spots on the unit circle. I get 1/2 as the answer, but not sure if I'm doing it right      Log On


   

Question 415687: Cos(-540 degrees) - tan 405 degrees.
I converted the degrees into radians to find the exact spots on the unit circle. I get 1/2 as the answer, but not sure if I'm doing it right?! Help! Thank you!
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
add 360 to -540 and you get -180 degrees.

add 360 again and you get +180 degrees.

cos(-540) is equivalent to cos (180).

cos(180) = -1.

since cos = adj/hyp, and since hyp is always +, then adj must be equal to -1.

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take 405 degrees and subtract 360 from it to get 45 degrees.

tan (405) is equivalent to tan (45).

tan(45) is equal to 1

you have cos(-540) minus tan(405) = -1 - (-1) which should be equal to -2 if I did this correctly.

if I use my calculator, i get4 cos(-540) = -1 and tan(405) = 1

this makes cos(-540) minus tan(405) equal to -1 - 1 = -2.

not sure where you got .5 from.

I also converted to pi radians and got the same answer.

-540 degrees is equal to -9.424777961 radians

405 degrees is equal to 7.068583471 radians

cos(-9.424777961 radians) is equal to -1.

tan(7.068583461 radians) is equal to 1.

-1 minus 1 is equal to -2.

picture of your angles is shown below.

***** picture not found *****

cos(-540) is equivalent to cos (-180) is equivalent to cos(180) = -1.

tan(405) is equivalent to tan(45) = 1.