为什么sin120度等于cos3o度 sin，tan，cos所对应的30度45度60度120度的值...
\u9ad8\u4e2d\u7269\u7406\u4e3a\u4ec0\u4e48\u662fcos120\u5ea6\u4e0d\u662fsin120\u5ea6\u8c22\u8c22\u5404\u4f4d\u8fd9\u662f\u6570\u5b66\u95ee\u9898
\u7269\u7406\u4f60\u8981\u6c42\u4ec0\u4e48\u8fb9\u4e0d\u5c31\u7528\u4ec0\u4e48\u51fd\u6570\u54af
\u7b80\u5355\u7684\u76f4\u89d2\u4e09\u89d2\u5f62 \u5df2\u77e5\u659c\u8fb9
\u6c42\u4e00\u5df2\u77e5\u89d2\u7684\u5bf9\u8fb9\u662f(\u659c\u8fb9\u00d7sin\u5df2\u77e5\u89d2)
\u6c42\u90bb\u8fb9\u662f(\u659c\u8fb9\u00d7cos\u5df2\u77e5\u89d2)\u54af
\u800c\u7269\u7406\u4e2d\u5927\u591a\u6570\u95ee\u9898\u4e2d\u7684\u5df2\u77e5\u91cf(\u77e2\u91cf \u6807\u91cf)\u90fd\u662f\u53ef\u4ee5\u5206\u89e3\u7684 \u6784\u5efa\u4e00\u4e2a\u76f4\u89d2\u4e09\u89d2\u5f62 \u5df2\u77e5\u91cf\u5c31\u6210\u4e86\u659c\u8fb9\u54af
\u91cf\u5417 \u529b\u554a \u901f\u5ea6\u554a \u4f4d\u79fb\u554a \u8def\u7a0b\u554a \u52a0\u901f\u5ea6\u554a ......
sin30\u00b0 = 2/1
sin45\u00b0 = (\u221a2)/2
sin60\u00b0 = (\u221a3)/2
sin120\u00b0 = (\u221a3)/2
cos30\u00b0 = (\u221a3)/2
cos45\u00b0 = (\u221a2)/2
cos60\u00b0 = 2/1
cos120\u00b0 = -2/1
tan30\u00b0 = (\u221a3)/3
tan45\u00b0 = 1
tan60\u00b0 = \u221a3
tan120\u00b0 = -(2-\u221a3)/2
=cos30° (应用诱导公式)。
说明：cos30° =√3/2。
绛旓細璇佹槑?姹傚煎惂,濡備笅 sin120º=sin(180º-60º)=sin60º=鈭3/2 cos120º=cos(180º-60º)= -cos60º= - 1/2
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