Question

How do you solve sin4x+sin2x=0 using the product and sum formulas?

Answer 1

sin2.2x+ sin2x=0

2sin2x.cos2x+sin2x=0

sin2x(2cos2x+1)=0

case 1---

sin2x=0

x=0,2π,4π,.....

case 2----

2cos2x+1=0

cos2x=-1/2

2x= 2π/3, 4π/3, 8π/3,.....

x=π/3,2π/3,4π/3,......

hope it help u

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