Tìm x,y,z nguyên:

\(x^2+y^2+z^2\le xy+3y+2z-4\)

Cho tanα = \(\dfrac{1}{2}\). Tính A= \(\dfrac{cos\alpha-sin\alpha}{cos\alpha+sin\alpha}\)

Cho tan. Tính A= \(\dfrac{cos\alpha-sin\alpha}{cos\alpha+sin\alpha}\)

Tính gtri bthuc

C = sin\(^2\)15\(^o\)+sin\(^2\)35\(^o\)+sin\(^2\)55\(^o\)+sin\(^2\)75\(^o\)

Tính gtri bthuc

A= sin 23\(^o\)\(-\) cos 67\(^o\)

B= \(\dfrac{tan70^0.tan45^0.tan20^0}{cot70^0.cot45^0.cot20^0}\)