sin6acos4a - sin4acos6a + sin2a

(Expand sin6acos4a as sin6a(cos4a) and sin4acos6a as sin4a(cos6a))

= sin2asin4acos2a + sin2a

(Expand sin6a as 2sin3acos3a)

= 2sin3acos3asin4acos2a + sin2a

(Simplify sin3a*cos3a as sin2(3a))

= 2sin(3a)sin(4a)*cos(2a) + sin(2a)

= 2(sin(3a)sin(4a)cos(2a)) + sin(2a)

= 2sin(3a + 4a)*cos(2a) + sin(2a)

= 2sin(7a)*cos(2a) + sin(2a)

So, the simplified expression is 2sin(7a)*cos(2a) + sin(2a)