Trigonometric equation \(\displaystyle{3}{{\sin}^{{2}}{\left({x}\right)}}+{{\sin}^{{2}}{\left({3}{x}\right)}}={3}{\sin{{x}}}\cdot{{\sin}^{{2}}{\left({3}{x}\right)}}\)

Tyson Mcneil

Tyson Mcneil

Answered question

2022-04-10

Trigonometric equation 3sin2(x)+sin2(3x)=3sinxsin2(3x)

Answer & Explanation

awalkbyfaithbzu6

awalkbyfaithbzu6

Beginner2022-04-11Added 21 answers

Write s=sinx. Then sin3x=3s4s4. Your original equation is
3s2+(3s4s3)2=3s(3s4s3)2
which simplifies to
s2(12+27s+24s272s316s4+48s5)=0
Numerical investigation suggests the bracket is nonzero on [1,1] so that s=0, or x=nπ (n integer) is the only solution.

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