Function cos−1(log2(x2+5x+8)) The function should exist when −1≤log2(x2+5x+8)≤1 We take only, log2(x2+5x+8)≤1 ⇒x2+5x+8≤(2)1 {∵−1≤log2(x2+5x+8) given imaginary values } ⇒x2+5x+6≤0 ⇒(x+2)(x+3)≤0
⇒x∈[−3,−2] Hence, the domain of the function is −3≤x≤−2