Let F1 and F2 be the two focuses of hyperbola x2a2 − y2b2 = 1 (a > 0, b > 0). If F1, F2 and P (0, 2b) are the three vertices of an equilateral triangle, then the eccentricity of hyperbola is______ .

Let F1 and F2 be the two focuses of hyperbola x2a2 − y2b2 = 1 (a > 0, b > 0). If F1, F2 and P (0, 2b) are the three vertices of an equilateral triangle, then the eccentricity of hyperbola is______ .

Let F1 (- C, 0), F2 (C, 0), then | f1p | = C2 + 4B2, ∵ F1, F2, P (0, 2b) are the three vertices of an equilateral triangle, ∵ C2 + 4B2 = 2c, ∵ C2 + 4B2 = 4C2, ∵ C2 + 4 (c2-a2) = 4C2, ∵ C2 = 4a2, ∵ E2 = 4, ∵ e = 2