设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+B)Sin(π/3-B)+sin2B 求角A的大小
来源:学生作业帮助网 编辑:作业帮 时间:2024/07/02 03:34:31
![设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+B)Sin(π/3-B)+sin2B 求角A的大小](/uploads/image/z/2960027-35-7.jpg?t=%E8%AE%BE%E2%96%B3ABC%E6%98%AF%E9%94%90%E8%A7%92%E4%B8%89%E8%A7%92%E5%BD%A2%2Cabc%E5%88%86%E5%88%AB%E6%98%AF%E5%86%85%E8%A7%92%2CABC%E6%89%80%E5%AF%B9%E8%BE%B9%E9%95%BF%2C%E5%B9%B6%E4%B8%94Sin2A%EF%BC%9Dsin%EF%BC%88%CF%80%2F3%2B%E8%AE%BE%E2%96%B3ABC%E6%98%AF%E9%94%90%E8%A7%92%E4%B8%89%E8%A7%92%E5%BD%A2%2Cabc%E5%88%86%E5%88%AB%E6%98%AF%E5%86%85%E8%A7%92%2CABC%E6%89%80%E5%AF%B9%E8%BE%B9%E9%95%BF%2C%E5%B9%B6%E4%B8%94Sin2A%EF%BC%9Dsin%EF%BC%88%CF%80%2F3%2BB%EF%BC%89Sin%EF%BC%88%CF%80%2F3%EF%BC%8DB%EF%BC%89%2Bsin2B+%E6%B1%82%E8%A7%92A%E7%9A%84%E5%A4%A7%E5%B0%8F)
设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+B)Sin(π/3-B)+sin2B 求角A的大小
设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+
设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+B)Sin(π/3-B)+sin2B 求角A的大小
设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+设△ABC是锐角三角形,abc分别是内角,ABC所对边长,并且Sin2A=sin(π/3+B)Sin(π/3-B)+sin2B 求角A的大小
sin²A=sin(π/3+B)sin(π/3-B)+sin²B
=(sinπ/3 cosB+cosπ/3 sinB)(sinπ/3 cosB-cosπ/3 sinB)+sin²B
=(sinπ/3cosB)²-(cosπ/3sinB)²+sin²B
=3cos²B/4-sin²B/4+sin²B
=(3cos²B+3sin²B)/4
=3/4
∵△ABC是锐角三角形 即A为锐角
∴sinA=√3/2
∴A=π/3