how do you solve problems like: cos[arctan(-1)] ?? thanks everyone



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nathanshields's profile pic

Posted on (Answer #1)

1. Tangent of what angle is -1?
2. What is cosine of this angle?

The tangent function is like the slope of a radius on the unit circle.  There are two that have a slope of -1: `135^o` and `315^o`

Let's just use the first one: `135^o` or `(3pi)/4` radians.

Take the cosine (visualize the adjacent and hypotenuse: `-sqrt(2)/2` and `1` ), and your answer is


Notice that if you used the other angle, your answer would be


So you check what domain you want your answer to be in.


agvickers's profile pic

Posted on (Answer #2)

in the problem all i was given was this, and it wants me to use the properties of inverse functions......i dont really understand it yet...


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