A right triangle rotated about its leg produces a cylinder. H - height of a cone, r - radius of a base (circle), s - slant of a cone\h5ex s = √(H^2+r^2). γ - apex angle. Volume of a cone: V = (1/3)πr^2H. The lateral surface of a cone after unfolded is circle sector. Base area: A_b = πr^2. Lateral surface area: A_l = πrl. Surface: S = A_b + A_l = πr^2 + πrs = πr(r+s). The cross section through its axis is a isosceles triangle. k - axis of a cone.