Mặc dù sự phát triển của Python có sự đóng góp của rất nhiều cá nhân, nhưng Guido van Rossum hiện nay vẫn là tác giả chủ yếu của Python. Ông giữ vai trò chủ chốt trong việc quyết định hướng phát triển của Python. | 165 Systems of Equations The trajectory of a satellite orbiting the earth is C R -------- --------- 1 e sin 9 a where R 9 are the polar coordinates of the satellite and C e and a are constants e is known as the eccentricity of the orbit . If the satellite was observed at the three positions 9 -30 0 30 R km 6870 6728 6615 determine the smallest R of the trajectory and the corresponding value of 9. 28. y 45 x V 61 m 300 m x A projectile is launched at O with the velocity v at the angle 9 to the horizontal. The parametric equation of the trajectory is x v cos 9 t y - 2 gt2 v sin 9 t where t is the time measured from instant of launch and g m s2 represents the gravitational acceleration. If the projectile is to hit the target at the 45 angle shown in the figure determine v 9 and the time of flight. 29. 166 Roots of Equations The three angles shown in the figure of the four-bar linkage are related by 150 cos 01 180 cos 0 2 - 200 cos 03 200 150 sin 01 180 sin 02 - 200sin 03 0 Determine 01 and 02 when 03 75 . Note that there are two solutions. 30. The 15-m cable is suspended from A and D and carries concentrated loads at B and C. The vertical equilibrium equations of joints B and C are T tan 0 2 tan 01 16 T tan ỡ 3 tan Ỡ 2 20 where T is the horizontal component of the cable force it is the same in all segments of the cable . In addition there are two geometric constraints imposed by the positions of the supports 4sin Ỡ1 6sin ỡ 2 5sin Ỡ 2 3 4 cos Ỡ1 6 cos Ỡ 2 5 cos Ỡ 3 12 Determine the angles 0 1 02 and 03. Zeroes of Polynomials Introduction A polynomial of degree n has the form Pn x a0 a 1 x a2x2 anxn where the coefficients a may be real or complex. We concentrate on polynomials with real coefficients but the algorithms presented in this section also work with complex coefficients. The polynomial equation Pn x 0 has exactly n roots which may be real or complex. If the coefficients are real the complex roots always occur in conjugate pairs xr ixị xr ixi .
