Решите пж с решением а,б,в,г

Решите задачу:

$1) \frac{sin^2t}{1+cost} = \frac{1-cos^2t}{1+cost} =\frac{(1-cost)(1+cost)}{1+cost}=1-cost \\ 2) sin^4t+cos^4t+2sin^2tcos^2t=(sin^2t+cos^2t)^2=1^2=1 \\ 3) \frac{cos^2t}{1+sint}+sint=\frac{1-sin^2t}{1+sint}+sint=\frac{(1-sint)(1+sint)}{1+sint}+sint= \\ =1-sint+sint=1 \\ 4)cos^4t+cos^2tsin^2t-cos^2t+1=cos^2t(cos^2t+sin^2t-1)+1= \\ =cos^2t(1-1)+1=1$