Buktikan sin 2 alfa/sin alfa = 1+ cos 2alfa/cos alfa

Ruas kiri
sin 2@ / sin @
= (2 . sin @ . cos @) /sin @
= 2 . cos @

Ruas kanan
(1 + cos 2@) / cos @
= (1 + 2cos²@ - 1) / cos @
= (2cos²@) / cos @
= 2 . cos @

*Terbukti*