f ( θ ) = sin θ {\displaystyle f(\theta )=\sin {\theta }} θ = 60 ∘ {\displaystyle \theta =60^{\circ }} f ( θ 2 ) {\displaystyle f({\frac {\theta }{2}})} sin ( 60 2 ) {\displaystyle \sin {({\frac {60}{2}})}} sin ( 30 ) = 1 2 {\displaystyle \sin {(30)}={\frac {1}{2}}}
