The intervals in which increases or decreases in are:

MATHEMATICS · Single correct · CBSE · Mathematics · Applications of Derivatives · Applications of Derivatives

Problem

The intervals in which f(x)=3cos⁡4x+10cos⁡3x+6cos⁡2x−3f(x)=3\cos^4x+10\cos^3x+6\cos^2x-3 increases or decreases in (0,π)(0,\pi) are: (1) Decreases on (π2,2π3)\left(\frac{\pi}{2},\frac{2\pi}{3}\right) and increases on (0,π2)∪(2π3,π)\left(0,\frac{\pi}{2}\right)\cup\left(\frac{2\pi}{3},\pi\right) (2) Decreases on (π2,π)\left(\frac{\pi}{2},\pi\right) and increases on (0,π2)\left(0,\frac{\pi}{2}\right) (3) Decreases on (0,π2)∪(2π3,π)\left(0,\frac{\pi}{2}\right)\cup\left(\frac{2\pi}{3},\pi\right) and increases on (π2,2π3)\left(\frac{\pi}{2},\frac{2\pi}{3}\right) (4) Decreases on (0,π2)\left(0,\frac{\pi}{2}\right) and increases on (π2,π)\left(\frac{\pi}{2},\pi\right)

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