Question

If $A={15}^{\circ }$, find the value of $4\cos 2A\cdot \sin 4A\cdot \tan 3A-1$.

Answer 1

Given: $A={15}^{\circ }$;

Hence, $4\cos 2A\cdot \sin 4A\cdot \tan 3A-1$

$=4\cos 2\left({15}^{\circ }\right)\cdot \sin 4\left({15}^{\circ }\right)\cdot \tan 3\left({15}^{\circ }\right)-1$

$=4\cos {30}^{\circ }\cdot \sin {60}^{\circ }\cdot \tan {45}^{\circ }-1$

$=4\frac{\sqrt{3}}{2}\times \frac{\sqrt{3}}{2}\times 1-1$

$=3-1$

$=2$