Answer:
9cos(46x) + 9cos(12x)
Step-by-step explanation:
18cos(29x)cos(17x)
According to Product-Sum identities
cos(α)cos(β)= (1/2)[cos(α+β)+cos(α-β)]
Putting α=29x and β=17x in Product-Sum identity we get
= 18×(1/2)[cos(29x+17x)+cos(29x-1`7x)]
Dividing 18 by 2 we get 9
= 9[cos(46x)+cos(12x)]
Multiplying 9 with both the terms we get
= 9cos(46x)+9cos(12x)
