Khong dùng máy tính cầm tay, hãy tính:
a) A = \(\dfrac{\sin33}{\cos57}+\dfrac{\tan32}{\cot58}-2\left(\sin20\cdot\cos70+\cos20\cdot\sin70\right)\)
b) B = \(\dfrac{\sin^215+\sin^275-\sin^212-\sin^218}{\cos^213+\cos^277+\cos^21+\cos^289}+\dfrac{2\cdot\tan55}{\cot35}\)