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Question Number 51167 by Tawa1 last updated on 24/Dec/18
Prove that:  (a)  If  ∣z_1  + z_2 ∣ = ∣z_1  − z_2 ∣,  the difference of the arguements of z_1   and z_2  is  (π/2)  (b)  If  arg{((z_1  + z_2 )/(z_1  − z_2 ))} = (π/2) ,   then    ∣z_1 ∣ = ∣z_2 ∣
Provethat:(a)Ifz1+z2=z1z2,thedifferenceofthearguementsofz1andz2isπ2(b)Ifarg{z1+z2z1z2}=π2,thenz1=z2
Answered by tanmay.chaudhury50@gmail.com last updated on 24/Dec/18
z_1 =a+ib   z_2 =c+id  a)∣(a+c)+i(b+d)∣=∣(a−c)+i(b−d)∣  (√((a+c)^2 +(b+d)^2 )) =(√((a−c)^2 +(b−d)^2 ))   2ac+2bd=−2ac−2bd  ac+bd=0  ac=−bd  (b/a)=−(c/d)  tanθ_1 =−cotθ_2   tanθ_1 =tan((π/2)+θ_2 )  θ_1 −θ_2 =(π/2)  b)((z_1 +z_2 )/(z_1 −z_2 ))  (((a+c)+i(b+d))/((a−c)+i(b−d)))  (((({(a+c)+i(b+d)}{(a−c)−i(b−d)})/((a−c)^2 +(b−d)^2 )) )/)  =(({(a^2 −c^2 +b^2 −d^2 )+i(−ab+ad−bc+cd+ab−bc+ad−cd})/((a−c)^2 +(b−d)^2 ))  tan(π/2)=((2ad−2bc)/((a−c)^2 +(b−d)^2 ))  (a−c)^2 +(b−d)^2 =0  so a=c  and b=d  ∣z_1 ∣=(√(a^2 +b^2 ))        =(√(c^2 +d^2 ))        =∣z_2 ∣
z1=a+ibz2=c+ida)(a+c)+i(b+d)∣=∣(ac)+i(bd)(a+c)2+(b+d)2=(ac)2+(bd)22ac+2bd=2ac2bdac+bd=0ac=bdba=cdtanθ1=cotθ2tanθ1=tan(π2+θ2)θ1θ2=π2b)z1+z2z1z2(a+c)+i(b+d)(ac)+i(bd){(a+c)+i(b+d)}{(ac)i(bd)}(ac)2+(bd)2={(a2c2+b2d2)+i(ab+adbc+cd+abbc+adcd}(ac)2+(bd)2tanπ2=2ad2bc(ac)2+(bd)2(ac)2+(bd)2=0soa=candb=dz1∣=a2+b2=c2+d2=∣z2
Commented by Tawa1 last updated on 24/Dec/18
God bless you sir
Godblessyousir
Commented by Tawa1 last updated on 24/Dec/18
Sir,  how is     − cotθ_2   =  tan((π/2) + θ_2 )  ??
Sir,howiscotθ2=tan(π2+θ2)??
Commented by tanmay.chaudhury50@gmail.com last updated on 24/Dec/18
tan((π/2)−θ)=cotθ  because (π/2)−θ=1st quadrant  but tan((π/2)+θ)=−cotθ  because ((π/2)+θ)  2nd quadrant
tan(π2θ)=cotθbecauseπ2θ=1stquadrantbuttan(π2+θ)=cotθbecause(π2+θ)2ndquadrant
Commented by Tawa1 last updated on 24/Dec/18
God bless you sir
Godblessyousir
Answered by peter frank last updated on 24/Dec/18
z_1 =x_1 +iy_1   z_2 =x_2 +iy_2   z_(1  ) +z_2 =(x_1 +x_(2 ) )+i(y_(1 ) +y_2 )  ∣z_(1  ) +z_(2 ) ∣=∣(x_1 +x_(2 ) )+i(y_(1 ) +y_2 )∣  (√((x_1 +x_2 )^2 +(y_1 +y_(2 ) )^2  )) ....(i)  ∣z_(1 ) −z_(2  ) ∣=(√((x_(1 ) −x_(2 ) )^2 +(y_1 −y_2 )^2 )) .....(ii)  ∣z_(1 ) −z_2 ∣=∣z_1 +z_2 ∣  ∣(√((x_(1 ) −x_(2 ) )^2 +(y_1 −y_2 )^2 )) =(√((x_(1 ) +x_2 )^2 +(y_1 +y_2 )^2 ))  2x_(1 ) x_2 −2y_1 y_2 =−2x_1 x_2 −2y_1 y_2   x_(1 ) x_(2  ) =−y_(1 ) y_2   1=−((y_1 /x_1 ) ).((y_2 /x_2 ))  1=−tan θ_(1  ) .tan θ_2   −tan^(−1) (π/4)=tan θ_1   tan^(−1) (π/4)=tan θ_(2  )   −2tan^(−1) (π/4)=tan (θ_1 −θ_(2 ) )  2.(π/4)=θ_1 −θ_2   (π/2)=θ_1 −θ_2   right or wrong?
z1=x1+iy1z2=x2+iy2z1+z2=(x1+x2)+i(y1+y2)z1+z2∣=∣(x1+x2)+i(y1+y2)(x1+x2)2+(y1+y2)2.(i)z1z2∣=(x1x2)2+(y1y2)2..(ii)z1z2∣=∣z1+z2(x1x2)2+(y1y2)2=(x1+x2)2+(y1+y2)22x1x22y1y2=2x1x22y1y2x1x2=y1y21=(y1x1).(y2x2)1=tanθ1.tanθ2tan1π4=tanθ1tan1π4=tanθ22tan1π4=tan(θ1θ2)2.π4=θ1θ2π2=θ1θ2rightorwrong?
Commented by Tawa1 last updated on 24/Dec/18
God bless you sir
Godblessyousir
Answered by peter frank last updated on 24/Dec/18
[arg(z_1 +z_(2 ) )−arg(z_1 −z_2 )=(π/2)  arg[(x_(1 ) +x_2 )+i(y_1 +y_2 )]−[arg(x_1 −x_2 +i(y_1 −y_2 )]  tan^(−1) (((y_(1 ) +y_2 )/(x_1 +x_2 )))−tan^(−1) (((y_1 −y_2 )/(x_1 −x_2 )))=(π/2)  (((y_(1 ) +y_2 )/(x_1 +x_2 )))+(((y_1 −y_2 )/(x_1 −x_2 )))÷[1−(((y_1 +y_2 )/(x_1 +x_2 ))).(((y_1 −y_2 )/(x_(1 ) −x_2 )))=(π/2)  (((y_(1 ) +y_2 )/(x_1 +x_2 )))+(((y_1 −y_2 )/(x_1 −x_2 )))÷[1−(((y_1 +y_2 )/(x_1 +x_2 ))).(((y_1 −y_2 )/(x_(1 ) −x_2 )))=(1/0)   x_1 ^2 −x_2 ^2 +y_2 ^2 −y_1 ^2 =0               x_1 ^2 +y_1 ^2 −x_2 ^2 −y_2 ^2 =0               x_1 ^2 +y_1 ^2 =x_2 ^2 +y_(2  ) ^2               ∣z_(1 ) ∣=∣z_2 ∣
[arg(z1+z2)arg(z1z2)=π2arg[(x1+x2)+i(y1+y2)][arg(x1x2+i(y1y2)]tan1(y1+y2x1+x2)tan1(y1y2x1x2)=π2(y1+y2x1+x2)+(y1y2x1x2)÷[1(y1+y2x1+x2).(y1y2x1x2)=π2(y1+y2x1+x2)+(y1y2x1x2)÷[1(y1+y2x1+x2).(y1y2x1x2)=10x12x22+y22y12=0x12+y12x22y22=0x12+y12=x22+y22z1∣=∣z2
Commented by Tawa1 last updated on 24/Dec/18
God bless you sir
Godblessyousir

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