[ti:trigonometric functions] [ar:天儿] [al:科学狂想曲] [by:] [offset:0] [00:00.00]trigonometric functions - 天儿 [00:02.26]词:天儿 [00:03.09]曲:天儿 [00:03.89] [00:10.60]When you first study math about 1234 [00:12.91]First study equation about xyzt [00:14.83]It will help you to think in a logical way [00:16.90]When you sing sine cosine cosine tangent [00:19.33]Sine cosine tangent cotangent [00:21.48]Sine cosine secant cosecant [00:23.61]Let's sing a song about trig-functions [00:25.72]sin(2π+α)=sinα [00:27.87]cos(2π+α)=cosα [00:30.02]tan(2π+α)=tanα [00:31.92]Which is induction formula1 and induction formula 2 [00:34.30]sin(π+α)= -sinα [00:36.46]cos(π+α)=-cosα [00:38.66]tan(π+α)= tanα [00:40.69]sin(π-α)= sinα [00:42.85]cos(π-α)=-cosα [00:45.02]tan(π-α)=-tanα [00:47.22]These are all those"name do not -change" [00:49.21]As pi goes to half pi the difference shall be huge [00:51.69]sin(π/2+α)=cosα [00:53.71]cos(π/2+α)=-sinα [00:55.76]tan(π/2+α)=-cotα [00:57.59] [00:58.11]sin(π/2-α)=cosα [01:00.00]cos(π/2-α)=sinα [01:02.14]tan(π/2-α)=cotα [01:04.04] [01:08.80]That is to say the odds will change evens are conserved [01:12.70]The notations that they get depend on where they are [01:16.97]But no matter where you are [01:19.36]I've gotta say that [01:21.47]If you were my sine curve I'd be your cosine curve [01:25.78]I'll be your derivative you'll be my negative one [01:30.09]As you change you amplitude I change my phase [01:33.98]We can oscillate freely in the external space [01:37.96] [01:38.54]As we change our period and costant at hand [01:42.61]We travel from the origin to infinity [01:46.54] [01:47.16]It's you sine and you cosine [01:51.46]Who make charming music around the world [01:55.55]It's you tangent cotangent [01:59.76]Who proclaim the true meaning of centrosymmetry [02:03.62] [02:47.09]You wanna measure width of a river height of a tower [02:49.42]You scratch your head which cost you more than an hour [02:51.45]You don't need to ask any"gods" or" master" for help [02:53.62]This group of formulas are gonna help you solve [02:55.75]sin(α+β)=sinα•cosβ+cosα•sinβ [02:59.00]cos(α+β)=cosα•cosβ-sinα•sinβ [03:02.32]tan(α+β)=(tanα+tanβ)/(1-tanα•tanβ) [03:05.49] [03:06.45]sin(α-β)=sinα•cosβ-cosα•sinβ [03:09.80]cos(α-β)=cosα•cosβ+sinα•sinβ [03:12.93]tan(α-β)=(tanα-tanβ)/(1+tanα•tanβ) [03:18.10]As you come across a right triangle you fell easy to solve [03:20.41]But an obtuse triangle gonna make you feel confused [03:22.52]Don't worry about what you do [03:23.65]There are always means to solve [03:24.70]As long as you master the sine cosine law [03:26.68] [03:30.25]At this moment I've got nothing to say [03:33.62] [03:34.14]As trig-functions rain down upon me [03:37.98] [03:38.69]At this moment I've got nothing to say [03:42.65]Let's sing a song about trig-functions [03:46.68] [03:47.22]Long live the trigonometric functions