Question Number 85623 by jagoll last updated on 23/Mar/20
$$\mathrm{prove}\:\mathrm{that}\: \\ $$$$\mathrm{sin}\:\mathrm{x}\:\mathrm{cos}\:\mathrm{2x}\:=\:\frac{\mathrm{1}}{\mathrm{4sin}\:\mathrm{4x}\:\mathrm{sec}\:\mathrm{x}} \\ $$
Answered by Henri Boucatchou last updated on 23/Mar/20
$${Wrong}\:{Sir}; \\ $$$${Take}\:\:{x}=\frac{\pi}{\mathrm{4}},\:\:\mathrm{0}\neq\frac{\mathrm{1}}{\mathrm{0}} \\ $$