Question

2
COS CA+B) =0, tan Ban find
Sind - cosB.​

Answer 1

Answer:

cos(A-B)/cos(A+B)+cos(C+D)/cos(C-D)=0

or (cosA.cosB+sinA.sinB)/(cosAcosB-sinAsinB)+(cosC.cosD-sinCsinD)/(cosC.cosD+sinCsinD)=0

or (1+tanA.tanB)/(1-tanA.tanB)+(1-tanC.tanD)/(1+tanCtanD)=0

or (1+tanA.tanB)/(1-tanA.tanB)= -(1-tanC.tanD)/(1+tanC.tanD)

Apply componendo and dividendo

or [(1+tanAtanB)+(1-tanAtanB)]/[(1+tanA.tanB)-(1-tanAtanB)]=[-(1-tanCtanD)+(1+tanCtanD)]/[-(1-tanCtanD)-(1+tanCtanD)].

or 2/2tanA.tanB=2tanCtanD/(-2)

or 1/tanAtanB=tanCtanD/(-1)

or tanA.tanB.tanC.tanD=-1 , Answer

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