How does √ (1 + sin α) turn into √ "(sin (α / 2) + cos (α / 2)) &# 178;" and | sin (α / 2) + cos (α / 2) | and which formula is used

How does √ (1 + sin α) turn into √ "(sin (α / 2) + cos (α / 2)) &# 178;" and | sin (α / 2) + cos (α / 2) | and which formula is used

1 = Sin & # 178; (A / 2) + cos & # 178; (A / 2) and Sina = 2Sin (A / 2) cos (A / 2)
Then:
1+sina
=sin²(a/2)+2sin(a/2)cos(a/2)+cos²(a/2)
=[sin(a/2)+cos(a/2)]²