SubArea: Analytic geometry in a planeLevel: BProject ID: 2010014609Source Problem: 9000151301Accepted: 0Clonable: 1Easy: 0Find the angle \(\varphi \) between the lines \(2x +1 = 0\) and \(x - y + 7 = 0\).\(45^{\circ }\)\(60^{\circ }\)\(90^{\circ }\)\(30^{\circ }\)
