P.o.t.W. #10 Solution
Method 1 double angle identity for cosine: \(\cos 2\alpha = 2{\cos ^2}\alpha - 1 substituting \(\theta for \(2\alpha gives: \(\cos \theta = 2{\cos ^2}\left( {\frac{\theta }{2}} \right) - 1\; from the cosine rule: \(\cos \theta = \frac{{{x^2} + {x^2} - {a^2}}}{{2xx}} = \frac{{2{x^2} - {a^2}}}{{2{x^2}}} substituting \(2{\cos ^2}\left( {\frac{\theta }{2}} \right) - 1 for \(\cos \theta , gives:...