Đề online: Luyện tập Công thức tổng thành tích và...

A \(\tan {10^0} + \tan {20^0}\)

B \(\tan {30^0}\)

C \(\cot {10^0} + \cot {20^0}\)

D \(\tan {15^0}\)

A \(\dfrac{{\sqrt 3 }}{2}\)

B \( - 1\)

C \(1\)

D \( - \sin \left( {a - b} \right)\)

A \(\sqrt 2 \sin x\)

B \( - \sqrt 2 \sin x\)

C \(\sqrt 2 \cos x\)

D \( - \sqrt 2 \cos x\)

A \(\sin a\sin b =  - \dfrac{1}{2}\left[ {\cos \left( {a + b} \right) - \cos \left( {a - b} \right)} \right]\)

B \(\sin a - \sin b = 2\sin \dfrac{{a + b}}{2}\cos \dfrac{{a - b}}{2}\)

C \(\tan 2a = \dfrac{{2\tan a}}{{1 - \tan a}}\)   

D \(\cos 2a = {\sin ^2}a - {\cos ^2}a\)

A \( - \dfrac{{113}}{{144}}\)

B \( - \dfrac{{115}}{{144}}\)

C \( - \dfrac{{117}}{{144}}\)

D \( - \dfrac{{119}}{{144}}\)

A \(\sin a + \sin b = 2\sin \dfrac{{a + b}}{2}\cos \dfrac{{a - b}}{2}\)

B \(\sin 2a - \sin 2b = 2\cos \left( {a + b} \right)\sin \left( {a - b} \right)\)

C \(\cos a - \cos b = 2\sin \dfrac{{a + b}}{2}\sin \dfrac{{a - b}}{2}\)

D \(\cos a - \cos b =  - 2\sin \dfrac{{a + b}}{2}\sin \dfrac{{a - b}}{2}\)

A \(M = 2\cos 2x\left( {\cos x + 1} \right)\)

B \(M = 4\cos 2x\left( {\dfrac{1}{2} + \cos x} \right)\)

C \(M = 2\cos 2x\cos \left( {\dfrac{x}{2} + \dfrac{\pi }{6}} \right)\cos \left( {\dfrac{x}{2} - \dfrac{\pi }{6}} \right)\)

D \(M = 4\cos 2x\cos \left( {\dfrac{x}{2} + \dfrac{\pi }{6}} \right)\cos \left( {\dfrac{x}{2} - \dfrac{\pi }{6}} \right)\)

A \(\cos {50^0}\)

B \(\cos {58^0}\)

C \(\sin {50^0}\)

D \(\sin {58^0}\)

A \(\cos x\)

B \(2\cos x - 1\)

C \(2\cos x\)

D \(\cos x - 1\)

A \(\tan 2x\)

B \(\sin x\)

C \(2\tan x\)

D \(2\sin x\)

A \(\dfrac{{23}}{{16}}\)             

B \(\dfrac{{21}}{{16}}\)

C \(\dfrac{7}{{16}}\)

D \(\dfrac{{23}}{8}\)

A \(M = 1 - 2{\cos ^2}a\)

B \(M = 1 - 2{\sin ^2}a\)

C \(M = \cos 4a\)

D \(M = \sin 4a\)

A \(\dfrac{2}{3}\)

B \(\dfrac{3}{2}\)

C \(\dfrac{3}{4}\)

D \(\dfrac{4}{3}\)

A \(\sin 2A + \sin 2B + \sin 2C = 4\cos A\cos B\cos C\)

B \(\sin 2A + \sin 2B + \sin 2C =  - 4\cos A\cos B\cos C\)

C \(\sin 2A + \sin 2B + \sin 2C = 4\sin A\sin B\sin C\)

D \(\sin 2A + \sin 2B + \sin 2C =  - 4\sin A\sin B\sin C\)

A \(1 + 2\cos x + \cos 2x = 4\cos x{\cos ^2}\dfrac{x}{2}\)

B \(\sin x\cos 3x + \sin 4x\cos 2x = \sin 5x\cos x\)

C \({\cos ^2}x + {\cos ^2}2x + {\cos ^2}3x - 1 = 2\cos 3x\cos 2x\cos x\)

D \({\sin ^2}x - {\sin ^2}2x - {\sin ^2}3x = 2\sin 3x\sin 2x\sin x\)

A \(\sin A + \sin B + \sin C = 4\cos \dfrac{A}{2}\cos \dfrac{B}{2}\cos \dfrac{C}{2}\)

B \(\cos A + \cos B + \cos C = 1 + 4\sin \dfrac{A}{2}\sin \dfrac{B}{2}\sin \dfrac{C}{2}\)

C \(\sin 2A + \sin 2B + \sin 2C = 4\sin A\sin B\sin C\)

D \(\cos 2A + \cos 2B + \cos 2C = 4\cos A\cos B\cos C\)

A \(\sqrt 3  - 2\cos x = 4\sin \left( {\dfrac{x}{2} + {{15}^0}} \right)\sin \left( {\dfrac{x}{2} - {{15}^0}} \right)\)

B \({\tan ^2}x - 3 = \dfrac{{4\sin \left( {x + \dfrac{\pi }{3}} \right)\sin \left( {x - \dfrac{\pi }{3}} \right)}}{{{{\cos }^2}x}}\)

C \({\sin ^2}7x - {\cos ^2}5x = \cos 12x\cos 2x\)

D \( + \sin x + \cos x = 2\sqrt 2 \cos \dfrac{x}{2}\cos \left( {\dfrac{x}{2} - \dfrac{\pi }{4}} \right)\)

A \(4\cos \left( {a - b} \right)\cos \left( {b - c} \right)\cos \left( {c - a} \right) = \cos 2\left( {a - b} \right) + \cos 2\left( {b - c} \right) + \cos 2\left( {c - a} \right)\)

B \(\cos 2x\sin 5x\cos 3x = \dfrac{{\sin 10x + \sin 6x + \sin 4x}}{4}\)

C \(\sin {40^0}\cos {10^0}\cos {8^0} = \dfrac{{\sin {{58}^0} + \sin {{42}^0} + \cos {8^0}}}{4}\)

D \(\sin a.\sin 2a.\sin 3a = \dfrac{{\sin 4a - \sin 6a + \sin 2a}}{4}\)

A \(2\)

B \(1\)

C \(4\)

D \(3\)

A Không tồn tại tam giác \(ABC\)

B Tam giác \(ABC\) đều

C Tam giác \(ABC\) cân

D Tam giác \(ABC\) vuông