1. In angle DEF , DM and EN are two medians. Prove that 3 (DF+EF) greater than 2(DM+EN).
Answers
Answer:
Step-by-step explanation:
Radio-controlled helicopter (also RC helicopter) is model aircraft which is distinct from a RC airplane because of the differences in construction, aerodynamics, and flight training. Several basic designs of RC helicopters exist, of which some (such as those with collective pitch control) are more maneuverable than others. The more maneuverable designs are often harder to fly, but benefit from greater aerobatic capabilities.[1]
Flight controls allow pilots to control the collective (or throttle, on fixed pitch helicopters), the cyclic controls (pitch and roll), and the tail rotor (yaw).[2] Controlling these in unison enables the helicopter to perform the same maneuvers as full-sized helicopters, such as hovering and backwards flight, and many other maneuvers that full-sized helicopters cannot, such as inverted flight (where collective pitch control provides negative blade pitch to hold heli up inverted, and pitch/yaw controls must be reversed by pilot).[3]
The various helicopter controls are effected by means of small servo motors, commonly known as servos. A solid-state gyroscope sensor is typically used on the tail rotor (yaw) control to counter wind- and torque-reaction-induced tail movement.[4] Most newer helicopters have gyro-stabilization on the other 2 axes of rotation (pitch and roll) as well. Such 3-axis gyro is typically called a flybarless controller, so-called because it eliminates the need for a mechanical flybar.[5]
The engines typically used to be methanol-powered two-stroke motors, but electric brushless motors combined with a high-performance lithium polymer battery (LiPo) are now more common and provide improved efficiency, performance, and lifespan compared to brushed motors, while decreasing prices bring them within reach of hobbyists. Gasoline and jet turbine engines are also used.[6]
Just like full sized helicopters, model helicopter rotors turn at high speeds and can cause severe injuries. Several deaths have occurred as recently as 2013.
Types of R/C helicopters
Radio gear
Construction
Competition
Commercial applications
Safety
Miniature helicopters
See also
References