Prove that 3tan2 45∘−sin2 60∘−(12)cot2 30∘+(18)sec2 45∘ = 1
LHS = 3(1)2−(√32)2−12(√3)2+18(√2)2
= 3−34−32+18(2)
= 3−34−32+14 = 12−3−6+14 = 1
Prove that:
sin2 72∘−sin2 60∘=√5−18
Prove
sin272° - sin260° = √5 -1/8