✓ 1 MARKS
MCQ
🔥 APPEARED IN 3 BOARD SETS
If $l_1, m_1, n_1$ and $l_2, m_2, n_2$ are direction cosines of lines $L_1$ and $L_2$ respectively and $\theta$ is the acute angle between them, then :
A
$\cos \theta = l_1 l_2 + m_1 m_2 + n_1 n_2$
B
$\sin \theta = l_1 l_2 + m_1 m_2 + n_1 n_2$
C
$\tan \theta = \frac{l_1}{l_2} + \frac{m_1}{m_2} + \frac{n_1}{n_2}$
D
$\cos \theta = | l_1 l_2 + m_1 m_2 + n_1 n_2 |$
01 // VERIFIED BOARD OCCURRENCES
| Year | Paper Code | Set | Position |
|---|---|---|---|
| CBSE 2026 | Series 65-3 | Set 1 | Question 16 |
| CBSE 2026 | Series 65-3 | Set 2 | Question 9 |
| CBSE 2026 | Series 65-3 | Set 3 | Question 2 |
02 // OFFICIAL CBSE MARKING SCHEME BREAKDOWN
- Step 1: Stating the fundamental formula / law statement (+1 Mark)
- Step 2: Intermediate mathematical substitution or proof steps (+1 Mark)
- Step 3: Correct final value or conclusion with mandatory SI units (+1 Mark)