# Find extreme value of cosx + cosy + cos(x+y)

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Find extreme value of cosx + cosy + cos(x+y)

by (187 points)

Also, we know that cos function attains its max value 1 at 0 radians.

so,  x = y = 0

• x+y = 0

Hence, the maximum value of cos x + cos y + cos (x+y) = 1 + (1)+1=3

Thus, the maximum value of cos x + cos y + cos (x+y) = 3

by (30.7k points)

We know that the cos function attains its minimum value as -1 at π radians.

• So, x = y = π
• x + y = 2π Now, we can write as;
• cos(x + y) = cos 2π = 1
• This is the min value of cos(x + y).

Thus, the minimum value of cos x + cos y + cos (x + y) = -1 + (-1 ) +1 = -1

Also, we know that cos function attains its max value 1 at 0 radians.

so,  x = y = 0

• x+y = 0

Hence, the maximum value of cos x + cos y + cos (x + y) = 1 + (1 )+1 = 3

Thus, the maximum value of cos x + cos y + cos (x + y) = 3 and minimum value = -1