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Đáp án + Giải thích các bước giải:

a,

- AB = BC . sin C = 4,5 . sin $35^{o}$ ≈ 2,58 (cm)

- AC = BC . cos C = 4,5 . cos $35^{o}$ ≈ 3,69 (cm)

- Góc B = $90^{o}$ - $35^{o}$ = $55^{o}$

b, 

- AC = AB . tan B = 3,1 . tan $65^{o}$ ≈ 6,65 (cm)

- BC = $\frac{AB}{cos B}$ = $\frac{3,1}{cos 65^{o}}$ ≈ 7,34 (cm)

- Góc C = $90^{o}$ - $65^{o}$ = $25^{o}$

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