一字马广告 怎么拍的:三角函数在模具制造中的应用

来源:百度文库 编辑:高考问答 时间:2024/05/07 09:04:10
请个位 从事模具行业的师傅 大哥们多多指导~ 俺就感激不尽了!!!

解:
由余弦定理a^2+b^2-c^2=2abcosC得:a^2+b^2=c^2+2abcosC
∵a^2+b^2=c^2+ab
∴cosC=1/2 ∴C=60°

sinAsinB
=(-1/2)[cos(A+B)-cos(A-B)]
=(-1/2)[cos(π-C)-cos(A-B)]
=(-1/2)[-cosC-cos(A-B)]
=(1/2)[cosC+cos(A-B)]
=(1/2)[(1/2)+cos(A-B)]
=(1/4)+[cos(A-B)]/2
∵sinAsinB=3/4
∴cos(A-B)=[(3/4)-(1/4)]×2=1 ∴A=B
∵A+B=180-60=120°
∴A=B=C=60° 为正三角形(等边三角形)

由余弦定理a^2+b^2-c^2=2abcosC得:a^2+b^2=c^2+2abcosC
∵a^2+b^2=c^2+ab
∴cosC=1/2 ∴C=60°

sinAsinB
=(-1/2)[cos(A+B)-cos(A-B)]
=(-1/2)[cos(π-C)-cos(A-B)]
=(-1/2)[-cosC-cos(A-B)]
=(1/2)[cosC+cos(A-B)]
=(1/2)[(1/2)+cos(A-B)]
=(1/4)+[cos(A-B)]/2
∵sinAsinB=3/4
∴cos(A-B)=[(3/4)-(1/4)]×2=1 ∴A=B
∵A+B=180-60=120°
∴A=B=C=60° 为正三角形(等边三角形)