Question

what is the maximum value of 3 - 7cos5x......plz give solution

Answer 1

max value is 11 . . . .

Answer 2

we have to find maximum value of (3 - 7cos5x)

we know, cosine function lies between -1 to 1
e.g., - 1 ≤ cos5x ≤ 1

multiplying with 7,

-7 ≤ 7cos5x ≤ 7

multiplying (-1), then, sign will be change of inequality.

(-1)(-7) ≥ (-1)7cos5x ≥ (-1)7

7 ≥ -7cos5x ≥ -7

now adding 3,

7 + 3 ≥ 3 - 7cos5x ≥ 3 - 7

10 ≥ 3 - 7cos5x ≥ - 4

or, -4 ≤ (3 - 7cos5x) ≤ 10

hence, maximum value of (3 - 7cos5x) = 10