Prove trigonometric identity

2008-03-22 3:41 am
Prove the identity for triangleABC(Show your step)

root(bcsinBsinC)=[(b^2)sinC+(c^2)sinB]/b+c

回答 (1)

2008-03-22 4:34 am
✔ 最佳答案
According sine Law

sinB/b=sinC/c

bsinC=csinB

So root(bcsinBsinC)=bsinC

Also
[(b^2)sinC+(c^2)sinB]/b+c
=[(bc)sinB+(bc)sinC]/(b+c)
=bc(sinB+sinC)/(b+c)
=(bc)(sinC/c)
=bsinC

So root(bcsinBsinC)=[(b^2)sinC+(c^2)sinB]/b+c

2008-03-21 20:38:25 補充:
sinC/c
=k
=k[(b+c)/(b+c)]
=(sinB+sinC)/(b+c)


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