[tex]\\ \sf\longmapsto \dfrac{1-cos2A}{1-sin2A}[/tex]
LHS
[tex]\boxed{\sf \dfrac{cosA}{sinA}=cotA}[/tex]
[tex]\\ \sf\longmapsto \dfrac{1-cos2A}{1-sin2A}[/tex]
[tex]\\ \sf\longmapsto 1-cot2A[/tex]
[tex]\\ \sf\longmapsto 1-\dfrac{1}{tan2A}[/tex]
[tex]\\ \sf\longmapsto \dfrac{tan2A-1}{tan2A}[/tex]
[tex]\\ \sf\longmapsto tan2A[/tex]
