Given:

f(x) is continuous at x = 0 & f(0) =

For f(x) to be continuous at x = 0,f(0)^– ₌ f(0) ^{+ =} f(0)

LHL = f(0)^– =

cos(–x) = cosx

f(0)^–

Since ,f(x) is continuous at x = 0 & f(0) =

k² = 1

k =