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how do you solve problems like: cos[arctan(-1)] ?? thanks everyone
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High School Teacher
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.
Posted by nathanshields on January 24, 2012 at 7:29 AM (Answer #1)
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