The given trigonometric equation can be written as
1−cos23x+sin4x=0
⇒sin23x+sin4x=0
⇒sin3x=0 and sinx=0 ,x∈[−25π,25π]
In given interval sinx=0 at x=−2π,−π,0,π,2π and these values are also satisfied by sin3x=0.
Hence total number of solutions is 5.
JEE Main 2019 — Mathematics Trigonometry
The number of solutions of the equation 1+sin4x=cos23x,x∈[−25π,25π] is:
Held on 12 Apr 2019 · Verified 6 Jul 2026.
5
7
3
4
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