问题描述:
lim x-0 1-cosx / x^2=1/2?用恒等变形怎么推呢
最佳答案:
1-cosx =1-[1-2sin²(x/2)]=2sin²(x/2)
当x→0时,sin²(x/2) x/2
则
1-cosx x²/2
即
lim x-0 1-cosx / x^2=1/2
limx-01-cosx/x^2=1/2?用恒等变形怎么推呢
问题描述:
lim x-0 1-cosx / x^2=1/2?1-cosx =1-[1-2sin²(x/2)]=2sin²(x/2)
当x→0时,sin²(x/2) x/2
则
1-cosx x²/2
即
lim x-0 1-cosx / x^2=1/2