The equation cos8x – bcos4 x + 1 = 0 will have a solution if... | MATH - SOLUTION OF QUADRATIC EQUATIONS AND NATURE OF ROOTS | SolveeIt | Solveeit

Today, August 18

Question

The equation cos⁸x – bcos⁴ x + 1 = 0 will have a solution if b belongs to

A

(–, 2]

B

[2, )

C

(–, –2]

D

None

Answer

(–, –2]

Explanation

Solution

Given equation can be written as

b = – $\left( \cos^{4}x + \frac{1}{\cos^{4}x} \right)$

£ –2 " x Ī R

Ž b Ī (–, –2]