Q&A Solve the systemx+y+\dfrac{1}{x}+\dfrac{1}{y} = \dfrac{9}{2} \\ xy+\dfrac{1}{xy} =\dfrac{5}{2} System of equations
Q&A Prove that: cos(π/15) cos(2π/15) cos(3π/15) cos(4π/15) cos(5π/15) cos(6π/5) cos(7π/15) = 1/128 \cos\dfrac{\pi}{15} \cos\dfrac{2\pi}{15} \cos\dfrac{3\pi}{15} \cos\dfrac{4\pi}{15} \cos\dfrac{5\pi}{15} \cos\dfrac{6\pi}{15} \cos\dfrac{7\pi}{15}=\dfrac{1}{128} Trigonometry
Q&A Prove the equality\cos^2\dfrac{\pi}{8}+\cos^2\dfrac{3\pi}{8}+\cos^2\dfrac{5\pi}{8}+\cos^2\dfrac{7\pi}{8}=2 Trigonometry
Q&A If A,B,C are three internal angles of a triangle, show that\sin^3 A \cos (B – C) + \sin^3 B \cos (C – A) + \sin^3 C \cos (A – B) = 3 \sin A \sin B \sin C Trigonometry
