锐角三角形ABC a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围锐角三角形ABC,内角A B C所对边分别为a b c ,a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围我求出A=60度
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![锐角三角形ABC a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围锐角三角形ABC,内角A B C所对边分别为a b c ,a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围我求出A=60度](/uploads/image/z/13435253-53-3.jpg?t=%E9%94%90%E8%A7%92%E4%B8%89%E8%A7%92%E5%BD%A2ABC+a%3D2%E6%A0%B9%E5%8F%B73+%E9%9D%A2%E7%A7%AFS%3D%E6%A0%B9%E5%8F%B73%2F4%28b%5E2%2Bc%5E2-a%5E2%29%E6%B1%82%281%29%E5%86%85%E8%A7%92A+%282%29%E5%91%A8%E9%95%BFl%E7%9A%84%E5%8E%BB%E5%80%BC%E8%8C%83%E5%9B%B4%E9%94%90%E8%A7%92%E4%B8%89%E8%A7%92%E5%BD%A2ABC%2C%E5%86%85%E8%A7%92A+B+C%E6%89%80%E5%AF%B9%E8%BE%B9%E5%88%86%E5%88%AB%E4%B8%BAa+b+c+%2Ca%3D2%E6%A0%B9%E5%8F%B73+%E9%9D%A2%E7%A7%AFS%3D%E6%A0%B9%E5%8F%B73%2F4%28b%5E2%2Bc%5E2-a%5E2%29%E6%B1%82%281%29%E5%86%85%E8%A7%92A+%282%29%E5%91%A8%E9%95%BFl%E7%9A%84%E5%8E%BB%E5%80%BC%E8%8C%83%E5%9B%B4%E6%88%91%E6%B1%82%E5%87%BAA%3D60%E5%BA%A6)
RtOB}PBS5HL#2Dǹ&Bw*wgpy)sv>4锐角三角形ABC a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围锐角三角形ABC,内角A B C所对边分别为a b c ,a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围我求出A=60度
锐角三角形ABC a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围
锐角三角形ABC,内角A B C所对边分别为a b c ,a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围
我求出A=60度 我需要详细的第二问锐角三角形ABC a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围锐角三角形ABC,内角A B C所对边分别为a b c ,a=2根号3 面积S=根号3/4(b^2+c^2-a^2)求(1)内角A (2)周长l的去值范围我求出A=60度
已知a=2√3,A=60°
根据正弦定理得
a/sinA=b/sinB=c/sinC
即2√3/sin60=b/sinB=c/sin(120-B)
故b=3sinB,C=3sin(120-B)
故b+c=3sinB+3sin(120-B)
=3[sinB+sin120cosB-cos120sinB]
=3[sinB+√3cosB/2+sinB/2]
=3[(3/2)sinB+(√3/2)cosB]
=3√3[√3/2sinB+(1/2)cosB]
=3√3sin(B+30)
在锐角三角形ABC中,
因0故30故1/2故(3√3)/2<3√3sin(B+30)<=3√3
即(3√3)/2则(7√3)/2