Given expression is 2sinAcos2A1−cosA11+cos2A
=2sinAcos2A1−cosA12cos2A
=sinA1−cosA
=2sinA2cosA22sin2A2
=cotA2
Prove that: (i) sinA+sin3AcosA−cos3A=cotA (ii) sin9A−sin7Acos7A−cos9A=cot8A (iii) sinA−sinBcosA−cosB=tanA−B2 (iv) sinA+sinBsinA−sinBtan(A+B2)cotA+B2 (v) cosA+cosBcosB−cosA=cotA+B2cotA−B2