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A \({a^2} = {b^2} + {c^2} - bc\cos A\)

B \({a^2} = {b^2} + {c^2} + bc\cos A\)

C \({a^2} = {b^2} + {c^2} - 2bc\cos A\)                      

D \({a^2} = {b^2} + {c^2} + 2bc\cos A\)

A \(a = 2R\cos A\)           

B \(a = 2R\sin A\)

C \(a = 2R\tan A\)

D \(a = R\sin A\)

A \(a\sin B = b\sin A\) 

B \(a\sin A = b\sin B\)

C \(a\cos B = b\cos A\)

D \(a\cos A = b\cos B\)

A \(bc = 2R.{h_a}\)

B \(ac = R.{h_b}\)

C \({a^2} = R.{h_a}\)

D \(ab = 4R.{h_c}\)

A \({h_a} = b\sin C\)      

B \({h_a} = c\sin B\)       

C \({h_b} = b\sin B\)

D \(c{h_c} = ab\sin C\)

A 10        

B \({{5\sqrt 6 } \over 2}\)           

C \(5\sqrt 3 \)       

D \(5\sqrt 2 \)

A \(2\sqrt {129} \)

B \(14\)

C \(98\)

D \(2\sqrt {69} \)

A \(12\sqrt 2 \)

B \(3\sqrt 2 \)       

C

\(2\sqrt 6 \)       

D \(6\sqrt 2 \)

A 25

B 5

C 6

D 7

A 30

B \(20\sqrt 2 \)

C \(10\sqrt 3 \)

D 20

A 2S

B 3S

C 4S

D 6S

A 5

B 10

C \({{10} \over {\sqrt 3 }}\)

D \(10\sqrt 3 \)

A \(3a\)

B \(2a\sqrt 2 \)

C \(2a\sqrt 3 \)

D \(a\sqrt 5 \)

A góc A nhọn

B góc A tù

C góc A vuông

D góc A là góc nhỏ nhất

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

B \({3 \over 8}\)

C \({4 \over 5}\)

D \({8 \over 9}\)

A \({2 \over 3}\)

B \({1 \over 3}\)

C \({-2 \over 3}\)

D \({1 \over 2}\)

A \(\sqrt 3 \)

B 4

C 2

D 1

A \(\beta  > \alpha \)

B \(\beta  < \alpha \)

C \(\beta  = \alpha \)

D \(\alpha  \le \beta \)