



 
Hi Alex. The symbol that looks like a 0 with a line through it is the greek letter "theta": θ. It is just a variable, you could as easily just call it x instead. For exponents, we usually type ^ (carat) in front. Anyway, the identity you want is the second one: sin^{2}θ + cos^{2}θ = 1. If we replace sin^{2}θ with the variable a, and cos^{2}θ with the variable b, then this is a + b = 1, and the question becomes: simplify 1  b. Well, a = 1  b. We can just subtract b from both sides of the equation. And what is a? it is sin^{2}θ. So 1  cos^{2}θ = sin^{2}θ. You see Alex, we can just use the usual rules of equations to solve the problem, the presence of the trig functions doesn't change that. Hope this helps,  


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