关于向量和三角函数已知向量a=(sin(wx+φ),2),b=(1,cos(wx+φ))(w>0,0<φ<π/4),函数f(x)=(a+b)·(a-b)【a,b均为向量】,y=f(x)的图像的相邻两对称轴之间的距离为2,且过点M(1,7/2)1.求函数f(x)2.若α∈(5π/6,4π/3),f(2α/π)=10/3,求sin(2α+4π/3)的值3.求f(0)+f(1)+f(3)+……+f(2011)的值
关于向量和三角函数
已知向量a=(sin(wx+φ),2),b=(1,cos(wx+φ))(w>0,0<φ<π/4),函数f(x)=(a+b)·(a-b)【a,b均为向量】,y=f(x)的图像的相邻两对称轴之间的距离为2,且过点M(1,7/2)
1.求函数f(x)
2.若α∈(5π/6,4π/3),f(2α/π)=10/3,求sin(2α+4π/3)的值
3.求f(0)+f(1)+f(3)+……+f(2011)的值
1.f(x)=(a+b)·(a-b)=a^2-b^2=sin(wx+φ)^2+4-cos(wx+φ)^2-1=3-cos(2wx+2φ)
T/2=2,2π/(2w)=4,w=π/4 -1/2=cos(π/2+2φ),φ=φ/12
f(x)=3-cos(π/2x+π/6)
2.cos(π/2*(2α/π)+π/6)=-1/3,sin(2α+4π/3)=-sin(2α+π/3)=-2sin(α+π/6)cos(α+π/6)
π sin(2α+4π/3)=-(4*2^(1/2))/9
3. f(i)+f(i+1)+f(i+3 )+f(i+4 )=0,2012/4=503,
f(0)+f(1)+f(3)+……+f(2011)=503×3=1509
a+b=sin(ωx+φ)+1
a-b=2-cos(ωx+φ)
f(x)=sin^2(ωx+φ)-1+4-cos^2(ωx+φ)=3-cos2(ωx+φ)
T/2=2
T=4
2π/2ω=T
ω=π/4
f(x)=3-cos(π/2x+2φ)
M(1,7/2)
f(1)=3-cos(π/2+2φ)=7/2
φ=1/12π
f(x)=3-cos(π/2x+π/6)
应该是这样,剩下的自己可以算了吧 :)
a+b=sin(ωx+φ)+1a-b=2-cos(ωx+φ)f(x)=sin^2(ωx+φ)-1+4-cos^2(ωx+φ)=3-cos2(ωx+φ)T/2=2T=42π/2ω=Tω=π/4f(x)=3-cos(π/2x+2φ)M(1,7/2)f(1)=3-cos(π/2+2φ)=7/2φ=1/12πf(x)=3-cos(π/2x+π/6)应该是...
(1)由y=f(x)的图像的相邻两对称轴之间的距离为2,知:T=4。
0<φ<π/4),且过点M(1,7/2)。
f(x)=sin^2(wx+φ)-cos^2(wx+φ)+3=- cos2*(wx+φ) +3 = - cos(π/2 *x+π/6)+3.
(2) 2α+π/3∈(2π,3π)
cos(2α+π/3)=2*cos)^2(α+π/6 )-1= -7/9.
sin(2α+4π/3)= - sin(2α+π/3)=- (4/3) *2^(1/2).
(3)
有规律可循,写出几项就可找出。