化简:sin(n∏-2/3∏)Xcos(n∏+4/3∏),n∈Z.
证明3^n-2^n>2^n,(n>1,n∈Z)
化简:(x+y-z)^3n*(z-x-y)^2n*(x-z+y)^5n(n为正整数)
求极限(sin(2/n)+cos(3/n))^(-n)
化简:1/(n+1)(n+2)+1/(n+2)(n+3)+1/(n+3)(n+4)
给定n∈N*,且n<100,(n-1)²/3+n/5∈Z.
证明sin(pi/n)*sin(2pi/n)*sin(3pi/n)*…sin((n-1)pi/n)=n/(2^(n-1)
已知函数f(n)=sin[(nπ)/6],n∈Z,则f(1)+f(2)+f(3)+···+f(102)=
1.已知 集合M={x/x=sin(nπ)/3,n∈z} 集合N={x/x=cos(nπ)/3,n∈z},M∩N等于
证明:1+2C(n,1)+4C(n,2)+...+2^nC(n,n)=3^n .(n∈N+)
[3n(n+1)+n(n+1)(2n+1)]/6+n(n+2)化简
化简(n+1)(n+2)(n+3)
i^4n=1,i^(4n+1)=i,i^(4n+2)=-1,i^(4n+3)=-i,当n∈Z时,能成立吗,书上是n∈N