What are the formulas of Sin & # 178; α = (1-cos (2 α)) / 2 and Sin & # 178; α = (1-sin (2 α)) / 2

What are the formulas of Sin & # 178; α = (1-cos (2 α)) / 2 and Sin & # 178; α = (1-sin (2 α)) / 2

The formula: the formula: ① cos2a = cos # 178; a-SiN \35; 178; a-SiN \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\a-1