+86 If x = arctan(-1/5) and x + y = 290 degrees, then cos y = ?
The "answer" that it shows is not a real answer and I'm still in need of one.
+37146 arctan(-.2) = 168.69 and 348.69 degrees
x+y = 290 then y = 121.31 degrees and -58.69 (301.31) degrees
then cos (y) = -.5196 and +.5196
+118677
If x = arctan(-1/5) and x + y = 290 degrees, then cos y
Firstly I find it totally confusing to call angles x and y.
So I am going to replace x with theta and y with alpha.
I am also going to assume that both the angles are positive and between 0 and 290.
\(tan\theta<0\) therefore theta must be in the 2nd or 4th quadrant but only the second one will work.
\(\alpha=290-\theta\\ cos(\alpha)\\ =cos(290-\theta)\\ =cos290cos\theta+sin290sin\theta\\ =cos70cos\theta -sin70sin\theta\\ =cos70\times \frac{-5}{\sqrt{26}} -sin70\times \frac{1}{\sqrt{26}}\\ = \frac{-5cos70-sin70}{\sqrt{26}} \\ \approx 0.5197\)
