introduction trigonometry

Question

sin + 2cos =1

then prove that 2sin - cos = 2

Answer 1

Graph the first equation to see that on the interval between 0 and 2π there are 2 roots. One is π/2 and, in fact, the second equation balances at x = π/2.

However, the second root is 5.64 and this does NOT satisfy the 2nd equation.