Kẻ AH⊥BC (H ∈ BC), Kẻ AH ⊥ BC (H ∈ BC), Kẻ AH⊥BC ( H∈BC), Kẻ AH BC (H ∈ BC), Kẻ AH⊥BC (H∈BC), kẻ AH⊥BC (H∈BC), Kẻ AH ⊥ BC (H ∈ BC ), Kẻ AH ⊥ BC ( H ∈ BC), Kẻ AH ⊥ BC ( H ∈ BC ), kẻ AH ⊥ BC(H ∈ BC)