a) 1 + sin a + cos a = 1 + sin a + cos a + sin a - sin a
= 1 + 2sin a + cos a - sin a
= 1 + 2sin a + sin (90° - a)
= (1 + sin(90°)) + 2sin a
= 2 sin a + 2
= 2(1 + sin a)

Ответ: 2(1 + sin a)

б) 1 - 4sin^2 a = (1 - 2sin a)(1 + 2sin a)

Ответ: (1 - 2sin a)(1 + 2sin a)