Question

Легкий ! вычислите tg8x если tg2x=1/4

Answer 1

$\tan8x=\frac{2\tan4x}{1-\tan^24x}\\\tan4x=\frac{2\tan2x}{1-\tan^22x}=\frac{2*\frac{1}{4}}{1-(\frac{1}{4})^2}=\frac{\frac{1}{2}}{\frac{15}{16}}=\frac{8}{15}\\\tan8x=\frac{2*\frac{8}{15}}{1-(\frac{8}{15})^2}=\frac{\frac{16}{15}}{\frac{161}{225}}=\frac{240}{161}$