[00:00:00] 三角函数之歌 (现场|Live|网友改编) - 南9
[00:03:00] 词：天儿
[00:04:00] 曲：天儿
[00:05:00] When you first study math about １２３４
[00:07:00] First study equation about xyzt
[00:09:00] It will help you to think in a logical way
[00:11:00] When you sing sine cosine cosine tangent
[00:13:00] Sine cosine tangent cotangent
[00:16:00] Sine cosine secant cosecant
[00:18:00] Let\'s sing a song about trig-functions
[00:20:00] sin(２π+α)=sinα
[00:22:00] cos(２π+α)=cosα
[00:24:00] tan(２π+α)=tanα
[00:26:00] Which is induction formula１ and induction formula ２
[00:28:00] sin(π+α)= -sinα
[00:31:00] cos(π+α)=-cosα
[00:33:00] tan(π+α)= tanα
[00:35:00] sin(π-α)= sinα
[00:37:00] cos(π-α)=-cosα
[00:39:00] tan(π-α)=-tanα
[00:41:00] These are all those \"name do not change\"
[00:43:00] As pi goes to half pi the difference shall be huge
[00:46:00] sin(π/２+α)=cosα
[00:48:00] cos(π/２+α)=-sinα
[00:50:00] tan(π/２+α)=-cotα
[00:52:00] sin(π/２-α)=cosα
[00:54:00] cos(π/２-α)=sinα
[00:56:00] tan(π/２-α)=cotα
[01:37:00] Let\'s go
[01:40:00] You wanna measure width of a river height of a tower
[01:42:00] You scratch your head which cost you more than an hour
[01:44:00] You don\'t need to ask any \"gods\" or\" master\" for help
[01:46:00] This group of formulas are gonna help you solve
[01:48:00] sin(α+β)=sinα•cosβ+cosα•sinβ
[01:52:00] cos(α+β)=cosα•cosβ-sinα•sinβ
[01:55:00] tan(α+β)=(tanα+tanβ)/(１-tanα•tanβ)
[01:58:00] sin(α-β)=sinα•cosβ-cosα•sinβ
[02:01:00] cos(α-β)=cosα•cosβ+sinα•sinβ
[02:05:00] tan(α-β)=(tanα-tanβ)/(１+tanα•tanβ)
[02:10:00] As you come across a right triangle you fell easy to solve
[02:13:00] But an obtuse triangle gonna make you feel confused
[02:16:00] Don\'t worry about what you do
[02:17:00] There are always means to solve
[02:18:00] As long as you master the sine cosine law
[02:23:00] At this moment I\'ve got nothing to say
[02:27:00] As trig-functions rain down upon me
[02:31:00] At this moment I\'ve got nothing to say
[02:36:00] Let\'s sing a song about trig-functions
[02:40:00] Long live the trigonometric functions