Prove that cos α cos 2α cos 4α .... cos 2 n +1 α = sin 2 n α 2 n sin α . Share with your friends Share 0 Mayur Pisode answered this Dear Student, Regards -1 View Full Answer Aman answered this bro in this case you have to use Principle mathematic induction (PMI) with trigonometry I w'll solve it and give to you by Saturday -2 Bandar answered this Hey! its very simple..Multiply and divide by 2 sin a and then consequently multiply and divide by 2. use the identity 2*cos a * sin a = sin 2a..... 1