f(x)=x−sin‌x f′(x)=1−cos‌x f′(x)=0⇒1−cos‌x=0 ⇒cos‌x=1 x=0,2π y=0 and y=2 are two parallel tangents and distance between them l1=2π Also other two parallel tangents are parallel to the line y=x f′(x)=1⇒1−cos‌x=1‌‌⇒cos‌x=0‌‌⇒x=‌
