Tìm vi phân toàn phần của các hàm số sau:
ln(x+√(x^2+y^2 ) ) ; ln(sin(y/x))

Ibelieve it's a. 2.2 - x = -10.85 (plz tell me if it's right : ) )

I'm a bit puzzled here because they did not provide you with any measures of the other angles, so i am unable to provide a theorem or postulate to support my answer, but i'd say 90 degrees because it looks closer to a right angle than anything.