Prove that, cos $\frac{3\pi }{13}$ + cos $\frac{5\pi }{13}$- 2 cos $\frac{9\pi }{13}$ cos $\frac{12\pi }{13}$=0
Prove that, cos $\frac{3\pi }{13}$ + cos $\frac{5\pi }{13}$- 2 cos $\frac{9\pi }{13}$ cos $\frac{12\pi }{13}$=0 Solution: L.H.S= cos $\frac{3\pi …