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ÂI¸Ñsin(270-a)=-cos a
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(1) sin¤J±Ó¼Æ¦r
0, 180, 360´Nø·|±NsinÅÜ°µcos
90, 270´Nn±NsinÅÜ°µcos
©OÓ±¡ªp
270-->sinnÅÜ°µcos
(2) 270-a «YÃäÓquadrant
§Ú¦aø»Ýn²zÃD¥Ø¤J±a>180«×
·Ó·í0<a<90¡]¥ô¦ó±¡ªp³£«YËÝ¡^
©Ò¥H270-a«Yquadrant III
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§Y«YT©O°Ï
-->±otan«Y¥¿¼Æ
-->sin«Yt¼Æ
-->©Ò¥Hn¥[t¸¹Íqcos
(1) sinÅÜcos
(2) ¥[t¸¹
-->sin(270-a)=(-cos a)