a. $tan(x+\frac{\prod }{6}).tan(x-\frac{\prod }{3})=1$
b. $tan\left [ \frac{\prod }{4}(sinx+1) \right ]=1$
c. $sin^{2}(5x+\frac{2\prod }{5})-cos^{2}(\frac{\prod }{4}+\prod )=0$
d. cosx + cos2x = sinx - sin2x
e. $\frac{tanx-1}{tanx+1}+cot2x=0$
- wtuan159 yêu thích