Question

Докажите равенство
tg(π/4+x)=(1+sin 2x)/cos2x

Answer 1

${\rm tg}\left(\frac{\pi}{4}+x\right)=\dfrac{\sin\left(\frac{\pi}{4}+x\right)}{\cos\left(\frac{\pi}{4}+x\right)}=\dfrac{2\sin^2\left(\frac{\pi}{4}+x\right)}{2\sin\left(\frac{\pi}{4}+x\right)\cos\left(\frac{\pi}{4}+x\right)}=\\ \\ \\ =\dfrac{2\cdot\dfrac{1-\cos\left(2\cdot \left(\frac{\pi}{4}+x\right)\right)}{2}}{\sin\left(2\cdot \left(\frac{\pi}{4}+x\right)\right)}=\dfrac{1-\cos\left(\frac{\pi}{2}+2x\right)}{\sin\left(\frac{\pi}{2}+2x\right)}=\dfrac{1+\sin 2x}{\cos 2x}$