Princess Sophie E: roro wrote: cos(a)=-0.4558
find a.
cos(a)=-0.4558
a=cos^-1(-0.4558)
=> a=117.1164195
Hi Sophie,
You have a second quadrant answer here but what about the one in the 3rd quadrant? Cos is negative there too.
I think that the easiest way to handle a question like this is to first solve
Cos
-1(0.4558) = B ( just had to use some letter so I used B for beta)
then think about which quadrants you need cos is neg in the second and the 3rd quad
then
a = 180 - B (second quad)
or
a = 180 + B (third quad)
+72 
+118687 
