9000151305

SubArea: 
Plane geometry
Level: 
B
Project ID: 
9000151305
Accepted: 
1
Clonable: 
0
Easy: 
0
Find the angle \(\varphi \) between the lines \(x + y + 1 = 0\) and \(x - y - 1 = 0\).
\(90^{\circ }\)
\(0^{\circ }\)
\(30^{\circ }\)
\(60^{\circ }\)