已知在三角形ABC中,已知a=根号3,b=根号2,角B=4分之派,解这个三角形。急用,快点! 20
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解答如下:
由正弦定理可得
a/sinA=b/sinB
即√3/sinA=√2/sin(π/4)
解得sinA=√3/2
所以在三角形中A=π/3
故C=π-π/4-π/3=5π/12
由余弦定理可得
c^2=a^2+b^2-2abcosC
=(√3)^2+(√2)^2-2√3*√2*cos5π/12
=5-2√6cos(π-π/4-π/3)
=5+2√6cos(-π/4-π/3)
=5+2√6cos(π/4+π/3)
=5+2√6(cosπ/4cosπ/3-sinπ/4sinπ/3)
=5+2√6[√2/2*(1/2)-√2/2*(√3/2)]
=5+2√6(√2/4-√6/4)
=5+√3-3
=2+√3
所以c=√(2+√3)=√[(2√3+4)/2]=√[(√3+1)^2/2]=(√3+1)/√2=(√6+√2)/2
即所求为A=π/3,C=5π/12,c=(√6+√2)/2
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由正弦定理可得
a/sinA=b/sinB
即√3/sinA=√2/sin(π/4)
解得sinA=√3/2
所以在三角形中A=π/3
故C=π-π/4-π/3=5π/12
由余弦定理可得
c^2=a^2+b^2-2abcosC
=(√3)^2+(√2)^2-2√3*√2*cos5π/12
=5-2√6cos(π-π/4-π/3)
=5+2√6cos(-π/4-π/3)
=5+2√6cos(π/4+π/3)
=5+2√6(cosπ/4cosπ/3-sinπ/4sinπ/3)
=5+2√6[√2/2*(1/2)-√2/2*(√3/2)]
=5+2√6(√2/4-√6/4)
=5+√3-3
=2+√3
所以c=√(2+√3)=√[(2√3+4)/2]=√[(√3+1)^2/2]=(√3+1)/√2=(√6+√2)/2
即所求为A=π/3,C=5π/12,c=(√6+√2)/2
~请首先关注【我的采纳率】
~如果不懂,请继续追问!
~如果你认可我的回答,请及时点击【采纳为最佳回答】按钮~
~如还有新的问题,在您采纳后可以继续求助我!
~您的采纳是我前进的动力~~
O(∩_∩)O,记得好评和采纳,互相帮助
祝学习进步!
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