4道三角恒等变换1.若f(x)是奇函数,且当x>0时,f(x)=x^2+sinx,则当x∈R时,f(x)为?A.x^2+sinx B.x^2-sinX C.‖x‖x+sinx D.‖x‖x-sinx2.函数f(x)=√3cos(3x-B)-sin(3x-B)是奇函数,则B等于?A.kπ B.kπ+π/6 C.kπ+π/3 D.kπ-π/
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![4道三角恒等变换1.若f(x)是奇函数,且当x>0时,f(x)=x^2+sinx,则当x∈R时,f(x)为?A.x^2+sinx B.x^2-sinX C.‖x‖x+sinx D.‖x‖x-sinx2.函数f(x)=√3cos(3x-B)-sin(3x-B)是奇函数,则B等于?A.kπ B.kπ+π/6 C.kπ+π/3 D.kπ-π/](/uploads/image/z/8946714-66-4.jpg?t=4%E9%81%93%E4%B8%89%E8%A7%92%E6%81%92%E7%AD%89%E5%8F%98%E6%8D%A21.%E8%8B%A5f%28x%29%E6%98%AF%E5%A5%87%E5%87%BD%E6%95%B0%2C%E4%B8%94%E5%BD%93x%3E0%E6%97%B6%2Cf%28x%29%3Dx%5E2%2Bsinx%2C%E5%88%99%E5%BD%93x%E2%88%88R%E6%97%B6%2Cf%28x%29%E4%B8%BA%3FA.x%5E2%2Bsinx+B.x%5E2-sinX+C.%E2%80%96x%E2%80%96x%2Bsinx+D.%E2%80%96x%E2%80%96x-sinx2.%E5%87%BD%E6%95%B0f%28x%29%3D%E2%88%9A3cos%283x-B%EF%BC%89-sin%EF%BC%883x-B%EF%BC%89%E6%98%AF%E5%A5%87%E5%87%BD%E6%95%B0%2C%E5%88%99B%E7%AD%89%E4%BA%8E%3FA.k%CF%80+B.k%CF%80%2B%CF%80%2F6+C.k%CF%80%2B%CF%80%2F3+D.k%CF%80-%CF%80%2F)
4道三角恒等变换1.若f(x)是奇函数,且当x>0时,f(x)=x^2+sinx,则当x∈R时,f(x)为?A.x^2+sinx B.x^2-sinX C.‖x‖x+sinx D.‖x‖x-sinx2.函数f(x)=√3cos(3x-B)-sin(3x-B)是奇函数,则B等于?A.kπ B.kπ+π/6 C.kπ+π/3 D.kπ-π/
4道三角恒等变换
1.若f(x)是奇函数,且当x>0时,f(x)=x^2+sinx,则当x∈R时,f(x)为?
A.x^2+sinx B.x^2-sinX C.‖x‖x+sinx D.‖x‖x-sinx
2.函数f(x)=√3cos(3x-B)-sin(3x-B)是奇函数,则B等于?
A.kπ B.kπ+π/6 C.kπ+π/3 D.kπ-π/3
3.已知sinA-sinB=1/2,则sin^3-cos^3= 多少?
4.tan20°+tan40°+√3 tan20°tan40°的值是?
以上各题要详解,以及涉及的知识点,
4道三角恒等变换1.若f(x)是奇函数,且当x>0时,f(x)=x^2+sinx,则当x∈R时,f(x)为?A.x^2+sinx B.x^2-sinX C.‖x‖x+sinx D.‖x‖x-sinx2.函数f(x)=√3cos(3x-B)-sin(3x-B)是奇函数,则B等于?A.kπ B.kπ+π/6 C.kπ+π/3 D.kπ-π/
1.f(x)=-f(-x)
令-x>0则
f(-x)=x²-sinx=-f(x)
∴f(x)=-x²+sinx (x∈(-00,0))
∴选C
2.∵f(x)为奇函数,
∴f(0)=0
即√3cosB+sinB=0
解得:π/3+B=kπ
∴B=kπ-π/3
选D
3.题目不是太清楚
4.tan20°+tan40°+√3 tan20°tan40°
∵tan60°=tan(20°+40°)=(tan20°+tan40°)/(1-tan20°*tan40°)
移项得:√3-√3tan20°*tan40°=tan20°+tan40°
移项得:√3=√3tan20°*tan40°+tan20°+tan40°