O is the orthocentre of `Delta ABC`, and if `/_BOC = 110^@`, then `/_BAC` will be

Options

A. `110^@`
B. ` 70^@`
C. `100^@`
D. `90^@`

Answer

To solve the problem, we need to find the angle \( \angle BAC \) given that \( O \) is the orthocenter of triangle \( ABC \) and \( \angle BOC = 110^\circ \).

### Step-by-Step Solution:

1. **Understanding the Orthocenter**: The orthocenter \( O \) of a triangle is the point where the three altitudes intersect. It has a special relationship with the angles of the triangle.

2. **Using the Angle Relationship**: For any triangle \( ABC \) with orthocenter \( O \), the following relationship holds:
\[ \angle BOC = 180^\circ - \angle BAC \]
This means that the angle formed by the lines \( OB \) and \( OC \) is supplementary to the angle at vertex \( A \).

3. **Substituting the Given Value**: We know from the problem that \( \angle BOC = 110^\circ \). We can substitute this value into the relationship:
\[ 110^\circ = 180^\circ - \angle BAC \]

4. **Solving for \( \angle BAC \)**: To find \( \angle BAC \), we rearrange the equation:
\[ \angle BAC = 180^\circ - 110^\circ \]
\[ \angle BAC = 70^\circ \]

5. **Final Answer**: Therefore, the measure of angle \( \angle BAC \) is \( 70^\circ \).

### Summary:
The angle \( \angle BAC \) is \( 70^\circ \).