The projectile flew out of the gun and hit a point with x coordinates horizontally and y coordinates vertically. Initial velocity of the projectile v. Find: a) the tangent of the angle formed by the gun barrel with the horizon; b) the boundary of the area of possible hit of the projectile; c) the lowest initial velocity of the projectile at which it can hit the point with coordinates x, y. Note. For the solution, use the trigonometric identity cos2φ1 = tg2φ+1.