Question

Помогите пожалуйста ​

Answer 1

$sin^{4}t + cos^{4}t + 2cos^{2} t =(sin^{2} t+cos^{2} t)*(sin^{2} t-cos^{2} t) + 2cos^{2} t =1*(sin^{2} t-cos^{2} t) + 2cos^{2} t = sin^{2} t+cos^{2} t = 1$