calculate the height AB of the airplane. Known: the airplane is at point B, the radar transmit at a speed of 3 108 m/s, echoes received from the aircraft after 1/3000 seconds. The transmitted angle of radar is 30. Algorithm: get the distance OB first, according to AB OB*sin30 get the height of the airplane due to round-trip time of radio is 1/3000 seconds, thus the Single-trip time is 1/3000/2, that is: OB 31081/3000/2 AB=OBsin300 B 300 A