1. \(\sqrt{\left(5+\sqrt{7}\right)^2}-\sqrt{8-2\sqrt{7}}\) .
2. \(\sqrt{\left(\sqrt{3}+1\right)^2}-\sqrt{4-2\sqrt{3}.}\)
3. \(\sqrt{11}-\sqrt{20-6\sqrt{11}}=3\)
4.\(\sqrt{41+12\sqrt{5}}-\sqrt{41-12\sqrt{5}}=2\sqrt{5.}\)
Cho 00 < x < 900. Chứng minh các đẳng thức sau:
1. sin6 x +cos6 x = 1 - 3sin2 x cos2 x.
2. sin4 x - cos4 x = 1 - 2cos2 x.
3. tan2 x - sin2 x = tan2 x.sin2x.
4. cot2 x - cos2 x = cot2 x.cos2 x.
5.\(\left(\sqrt{\dfrac{1+sinx}{1-sinx}}-\sqrt{\dfrac{1-sinx}{1+sinx}}\right)^2\) = 4 tan2 x.
6.\(\left(\sqrt{\dfrac{1+cosx}{1-cosx}}-\sqrt{\dfrac{1-cosx}{1+cosx}}\right)^2\) = 4 cot2 x.