5) Prove that Cos 70°Cos10° + Sin 70°Sin10° = 1/2 Share with your friends Share 7 Priyanka Kedia answered this L.H.S.=cos700cos100+sin700sin100 =cos700-100 Using the formula, cosAcosB+sinAsinB=cosA-B =cos600 =12 =R.H.S.Hence Proved. 12 View Full Answer