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Question

ABC is a triangle. BI and CI are angle bisectors of $\angle ABC$ and $\angle ACB$. $\angle BAC = 45^\circ$. Find the measure of $\angle BIC$.

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper PDF (31-Jan-2021) (Shift 1)
The correct answer is
$112.5^\circ$

To find the measure of \(\angle BIC\) in triangle \(ABC\) where \(BI\) and \(CI\) are angle bisectors of \(\angle ABC\) and \(\angle ACB\), we can use the following geometric property of angle bisectors:

The measure of the angle formed by two internal angle bisectors of a triangle, namely \(\angle BIC\), is given by:

\(\angle BIC = 90^\circ + \frac{1}{2} \angle BAC\).

Given that \(\angle BAC = 45^\circ\), we can substitute this value into the formula:

\(\angle BIC\) = 90° + 0.5 × 45°
\(\angle BIC\) = 90° + 22.5°
\(\angle BIC\) = 112.5°

Hence, the measure of \(\angle BIC\) is \(112.5^\circ\).

The correct answer is \(112.5^\circ\).

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