wat+phra+singh+temple

毋哄复4171一道电路题,做的结果和答案不符,已知u1=220倍根号2sin(wt+60度)V,u2=220倍根号2cos(wt+30度)V,求u1+u2和u1 - u2. -
齐夜符18140141384 ______[答案] u1+u2=220*(根号2)*sin(ω t+60度)+220*(根号 2)*cos(ω t+30度) =220*(根号 2)*[ sin(ω t+60度)+cos(ω t+30度)] =220*(根号 2)*{[sin(ω t)*cos60度+sin60度*cos(ω t)]+[cos(ω t)*cos(30度)-sin(ω t)*sin(30度)]} =220*(根号 2)*(根号3)*...

毋哄复4171利用欧拉公式证明cosθ+cos2θ+cos3θ+···+cosnθ= - 1/2+sin(n+1/2)θ/sin(θ/2) -
齐夜符18140141384 ______[答案] cosθ=[e^(iθ)+e^(-iθ)]/2 cos2θ=[e^(2iθ)+e^(-2iθ)]/2 cos3θ=[e^(3iθ)+e^(-3iθ)]/2 ... cosnθ=[e^(inθ)+e^(-inθ)]/2

毋哄复4171证明(1+cosα+sinα+2sinαcosα)/(1+sinα+cosα)=sinα+cosα -
齐夜符18140141384 ______[答案] 1+cosα+sinα+2sinαcosα =cos²α+sin²α+cosα+sinα+2sinαcosα =(sinα+cosα)²+cosα+sinα =(cosα+sinα)(1+sinα+cosα) (1+cosα+sinα+2sinαcosα)/(1+sinα+cosα)=sinα+cosα

毋哄复4171sinθ+sin2θ/1+cosθ+cos2θ= -
齐夜符18140141384 ______[答案] (sinθ+sin2θ)/(1+cosθ+cos2θ) =(sinθ+sin2θ)/(1+cosθ+2cos²θ-1) =(sinθ+2sinθcosθ)/(cosθ+2cos²θ) =sinθ(1+2cosθ)/[cosθ(1+2cosθ)] =sinθ/cosθ =tanθ

毋哄复4171三角函数 化简题化简cos(π/3 +α) +sin(π/6 +α) -
齐夜符18140141384 ______[答案] cos(π/3 +α) +sin(π/6 +α) =cos(π/3)cosα-sin(π/3)sinα+sin(π/6)cosα+cos(π/6)sinα =1/2 cosα-√3/2 sinα+1/2 cosα+√3/2sinα =cosα

毋哄复4171cosθ+sinθ=√2sin(θ+π/4)这个公式怎么推导出来的 -
齐夜符18140141384 ______[答案] cosθ+sinθ==√2(sin45*cosθ+cos45*sinθ)==√2sin(θ+π/4)

毋哄复4171已知函数f(x)=sinx+sin(x+π/2),求f(x)的最小正周期,f(x)的最值,若f(x)=3/4,求sin2x? -
齐夜符18140141384 ______[答案] f(x)=sinx+sin(x+π/2)=sinx+cosx 故f(x)的最小正周期是2π f^2(x)=(sinx+cosx)^2=1+sin2x sin2x=-7/16

毋哄复4171a+b+c=2π 证明sina+sinb+sinc=4sina/2sinb/2sinc/2 -
齐夜符18140141384 ______[答案] (a+b)/2= π -c/2 sina+sinb+sinc =2sin(a+b)cos(a-b)+2sin(c/2)cos(c/2) =2sin[(a+b)/2]cos[(a-b)/2]-2sin[(a+b)/2]cos[(a+b)/2] =2sin[(a+b)/2] [cos(a-b)/2-cos[(a+b)/2] =2sinc/2 *[cos(a-b)/2-cos[(a+b)/2] =4sina/2sinb/2sinc/2 得证.

毋哄复4171sinα+sinβ=2分之根号2,求cosα+cosβ取值范围答案选项里都有14分之根号14, -
齐夜符18140141384 ______[答案] sinα+sinβ=2分之根号2, 令cosα+cosβ=k 分别平方并相加 由sin²x+cos²x=1 所以2+2(cosαcosβ+sinαsinβ)=1/2+k² cos(α-β)=cosαcosβ+sinαsinβ=(k²-3/2)/2 -1-1-1/2即0所以-√14/2解析看不懂?免费查看同类题视频解析查看解答更多答案(2)

毋哄复4171解三角形中a与sinA的转换,什么时候可以把a代换成SINA,什么时候不可以呀?如三角形ABC中,a.sinA+sinB+bcos平方A=根号2.两个可以转换的条件是什... -
齐夜符18140141384 ______[答案] 这个不能转换的 a/sinA=b/sinB=c/sinC 所以假设每一项都有sin或者每一项都有边长就行 比如a+b=2c 就是sinA+sinB=2sinC 或者sin²A+sin²B+sinAsinB=sin²C 则a²+b²+ab=c²