= . (1)
I don't know exactly what is 10: radians or degrees? Will suppose degrees.
We all know that
= .
Combining this with (1), you will get
= .
It implies that
= . (2)
Not exactly, because you should remember about +/- and other similar additional terms,
but I am going to give only the "naive" solution here.
From (2) you have
= 90° +10° = 100°. Hence = .100°.
