(1)∵∠A=76°,
∴∠ABC+∠ACB=180°-76°=104°,
∴∠OBC+∠OCB=1/2×104°=52°
∴∠BOC=180°-52°=128°;
(2)∠BOC=90°+1/2∠A.
理由如下:
∵∠BOC=180°-∠OBC-OCB,
=180°-(∠OBC+∠OCB),
=180°-(∠ABC+∠ACB),
=180°-(180°一∠A),
=180°-90°+1/2∠A,
=90°+1/2∠A.
即∠BOC=90°+1/2∠A.
(1)∵∠A=76°,
∴∠ABC+∠ACB=180°-76°=104°,
∴∠OBC+∠OCB=1/2×104°=52°
∴∠BOC=180°-52°=128°;
(2)∠BOC=90°+1/2∠A.
理由如下:
∵∠BOC=180°-∠OBC-OCB,
=180°-(∠OBC+∠OCB),
=180°-(∠ABC+∠ACB),
=180°-(180°一∠A),
=180°-90°+1/2∠A,
=90°+1/2∠A.
即∠BOC=90°+1/2∠A.