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← JEE Main 2022 · 29 Jun · Shift 2
MathematicsInteger+4 / -1Question 24 of 90

JEE Main 2022 · 29 Jun · Shift 2, Mathematics question 24

The number of solutions of the equation sin⁡x=cos⁡2x\sin x=\cos^2x in the interval (0,10)(0,10) is ______.

Answer and worked solution

Official answer: 4

Quadratic. sin⁡2x+sin⁡x−1=0\sin^2x+\sin x-1=0 gives sin⁡x=5−12≈0.618\sin x=\frac{\sqrt5-1}2\approx0.618.

In (0,10)(0,10). Two solutions in (0,π)(0,\pi) and two in (2π,3π)(2\pi,3\pi) (both below 10, since the larger is 3π−0.67≈8.753\pi-0.67\approx8.75). Total 4.

Answer: 4