radian
Baidu Encyclopedia definition: The method of measuring the angle of the corresponding central angle by the ratio of arc length to radius is called the radian system, which is expressed by the symbol rad and pronounced as radians. The central angle of the arc equal to the length of the radius is called the angle of 1 radian. Since the ratio of the length of the arc to the radius of the circle does not change due to the size of the circle, the number of radians is also a quantity that has nothing to do with the radius of the circle.
Conversion between degrees and radians
180度＝π弧度
由此
1度＝π/180 弧度 ( ≈0.017453弧度 )
因此，
弧度＝度×π/180
例如：
90°＝90×π/180 ＝π/2 弧度
60°＝60×π/180 ＝π/3 弧度
45°＝45×π/180 ＝π/4 弧度
30°＝30×π/180 ＝π/6 弧度
120°＝120×π/180 ＝2π/3 弧度
frequency
Baidu Encyclopedia Definition: The number of times a substance completes periodic changes in 1s is called frequency, which is often expressed as f. In order to commemorate the contribution of the German physicist Hertz, people named the unit of frequency Hertz, abbreviated as "Hertz", and the symbol is HZ.
Frequency is the number of times that periodic changes are completed per unit time, and it is a quantity that describes the frequency of periodic motion.
The basic unit of frequency in physics is Hertz (Hz), abbreviated as Hertz, and kilohertz (kHz), megahertz (MHz) or gigahertz (GHz) are also commonly used as the unit. 1kHz=1000Hz, 1MHz=1000000Hz, 1GHz=1000MHz.
The reciprocal of the period is called the frequency, which is represented by the symbol f, where f = 1/T.
Angular frequency [4] The relationship between ω and frequency f is: ω = 2πf.
Angular frequency
Angular frequency, also called circular frequency, represents the radians of the phase angle that changes per unit time. Angular frequency is a physical quantity that describes how fast an object vibrates. It is related to the inherent properties of the vibration system and is often represented by the symbol ω. In the International System of Units, the unit of angular frequency is radians per second (rad/s). Every object has a frequency that is determined by its nature and has nothing to do with the amplitude, called the natural angular frequency.
Phase
Phase describes the measurement of signal waveform change, usually in degrees (angle), also known as phase angle. When the signal waveform changes in a periodic manner, the waveform cycle is 360°.
In the function y=Acos(ωx+φ), ωx+φ is called the phase . x = 0, φ is called the initial phase .
In alternating current, phase is a physical quantity that reflects the state of alternating current at any time. The magnitude and direction of alternating current changes over time. For example, sinusoidal alternating current, its formula is i=Isin2πft. i is the instantaneous value of the alternating current, I is the maximum value of the alternating current, f is the frequency of the alternating current, and t is the time. Over time, the AC current can change from zero to the maximum value, from the maximum value to zero, and from zero to the negative maximum, and from the negative maximum to zero. In the trigonometric function, 2πft is equivalent to radians, which reflects the state of the alternating current at any time, whether it is increasing or decreasing, whether it is positive or negative, and so on. Therefore, 2πft is called phase, or phase.
Phase angle
Baidu Encyclopedia: In the expression of the instantaneous value of alternating current, the amount after the sine (or cosine) symbol is equivalent to the angle, which is called the phase angle of alternating current, also called phase, phase or circumferential phase. For example, the expression of the instantaneous value e of the sinusoidal AC electromotive force is:
e=Emsin(ωt+ψ0)
where (ωt+ψ0) is the phase angle of the sinusoidal AC electromotive force. When t=0, the phase angle is equal to ψ0, which is called the initial phase angle, or the initial phase for short . The difference between the initial phase angles of two sine quantities with the same frequency is called the phase angle difference or phase difference. Two sine quantities whose phase angle difference is equal to zero are called in-phase; two sine quantities whose phase angle difference is 180° are called antiphase; two sine quantities whose phase angle difference is 90° are called quadrature