> 数学 >
2.设f(x)=(sin^4 x-cos^4 x-5)/(cos2x+2).(a)证明f(x)= 3/(2 sin^2 x-3) -1 (b)求f(x)的范围
人气:401 ℃ 时间:2020-06-24 09:30:27
解答
f(x)=[(sin^2 x+cos^2 x)(sin^2 x-cos^2 x)-5]/[1-2sin^2 x+2]=(sin^2 x-cos^2 x-5)/[3-2sin^2 x]=(2sin^2 x-3-3)/[3-2sin^2 x]=3/(2 sin^2 x-3) -1得证当sin^2 x=1时,f(x)有最小值-4,当sin^2 x=0时,f(x)有最大值-2 ...
推荐
猜你喜欢
© 2025 79432.Com All Rights Reserved.
电脑版|手机版