1. By squaring both sides of the identity sin^2 A + cos^2 A=1, or otherwise, show that sin^4 A + cos^4=(1/4)(3+cos4A). Hence find the possible greatest value and the smallest value of sin^4 θ + cos^4 θ
2. Given that A, B, C are the angles of a triangle, show that tan C= (tanA+tanB)/(tanAtanB-1)