Answer:
1st : neither linear nor nonlinear
2nd: nonlinear
3rd: linear
4th: both linear and nonlinear
An obtuse angle would be an angle more then 90 degrees.
So if you add two angles together, it could be less then 90 degrees, such as 30 + 50 = 80 degrees.
However, it can also be more then 90 degrees, or an obtuse angle, for example 60 + 50 = 110 degrees.
So it's sometimes.
the anwser is 36...................