Through the focus F of the parabola y ^ 2 = 4x, make a straight line intersection parabola with an inclination angle of θ, and use θ to represent the length of AB at two points ab

Through the focus F of the parabola y ^ 2 = 4x, make a straight line intersection parabola with an inclination angle of θ, and use θ to represent the length of AB at two points ab

Let a (x1, Y1), B (X2, Y2) use the definition of parabola, then | AF | = X1 + 1, | BF | = x2 + 1 | | ab | = X1 + x2 + 2 straight line is y = Tan θ (x-1) substituted into the parabola equation, then Tan |; 178; θ (x-1) # 178; = 4x is tan | | 178; θ x # 178; - (2tan |; 178; θ + 4