为什么sin和cos可以这么变换 sin cos之间怎么转换？
cos \u600e\u4e48\u53d8\u6210sin\u7684cos\u53ef\u4ee5\u5229\u7528\u4e09\u89d2\u51fd\u6570\u516c\u5f0fsin(\u03c0/2-a)=cosa\u6216\u8005sin(\u03c0/2+a)=cosa\uff0c\u8f6c\u6362\u6210sin\u3002
\u03c0/2\u00b1\u03b1\u4e0e\u03b1\u7684\u4e09\u89d2\u51fd\u6570\u503c\u4e4b\u95f4\u7684\u5173\u7cfb\uff1a
sin\uff08\u03c0/2+\u03b1\uff09=cos\u03b1
sin\uff08\u03c0/2\uff0d\u03b1\uff09=cos\u03b1
cos\uff08\u03c0/2+\u03b1\uff09=\uff0dsin\u03b1
cos\uff08\u03c0/2\uff0d\u03b1\uff09=sin\u03b1
tan\uff08\u03c0/2+\u03b1\uff09=\uff0dcot\u03b1
tan\uff08\u03c0/2\uff0d\u03b1\uff09=cot\u03b1
cot\uff08\u03c0/2+\u03b1\uff09=\uff0dtan\u03b1
cot\uff08\u03c0/2\uff0d\u03b1\uff09=tan\u03b1
\u5e38\u7528\u4e09\u89d2\u51fd\u6570
1\u3001\u4e07\u80fd\u516c\u5f0f
sina=[2tan\uff08a/2\uff09]/[1+tan²\uff08a/2\uff09]
cosa=[1-tan²\uff08a/2\uff09]/[1+tan²\uff08a/2\uff09]
tana=[2tan\uff08a/2\uff09]/[1-tan²\uff08a/2\uff09]
2\u3001\u964d\u5e42\u516c\u5f0f
sin²\u03b1=[1-cos\uff082\u03b1\uff09]/2
cos²\u03b1=[1+cos\uff082\u03b1\uff09]/2
tan²\u03b1=[1-cos\uff082\u03b1\uff09]/[1+cos\uff082\u03b1\uff09]
3\u3001\u4e09\u89d2\u548c
sin\uff08\u03b1+\u03b2+\u03b3\uff09=sin\u03b1\u00b7cos\u03b2\u00b7cos\u03b3+cos\u03b1\u00b7sin\u03b2\u00b7cos\u03b3+cos\u03b1\u00b7cos\u03b2\u00b7sin\u03b3-sin\u03b1\u00b7sin\u03b2\u00b7sin\u03b3
cos\uff08\u03b1+\u03b2+\u03b3\uff09=cos\u03b1\u00b7cos\u03b2\u00b7cos\u03b3-cos\u03b1\u00b7sin\u03b2\u00b7sin\u03b3-sin\u03b1\u00b7cos\u03b2\u00b7sin\u03b3-sin\u03b1\u00b7sin\u03b2\u00b7cos\u03b3
tan\uff08\u03b1+\u03b2+\u03b3\uff09=\uff08tan\u03b1+tan\u03b2+tan\u03b3-tan\u03b1\u00b7tan\u03b2\u00b7tan\u03b3\uff09\u00f7\uff081-tan\u03b1\u00b7tan\u03b2-tan\u03b2\u00b7tan\u03b3-tan\u03b3\u00b7tan\u03b1\uff09
\u9898\u76ee\u662fsinx\u5417
\u5148\u628a2cos(\u03c0
x/2)\u7684\u56fe\u50cf\u4e0a\u7684\u70b9\u7684\u7eb5\u5750\u6807\u7f29\u5c0f\u4e3a\u539f\u6765\u7684\u4e00\u534a\uff0c\u7136\u540e\u5728\u53d8\u6362\u6a2a\u5750\u6807
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