WBJEE · Maths · Determinants
If \(P, Q\) and \(R\) are angles of \(\Delta P Q R\), then the value of \(\left|\begin{array}{ccc}-1 & \cos R & \cos Q \\ \cos R & -1 & \cos P \\ \cos Q & \cos P & -1\end{array}\right|\) is equal to
- A -1
- B 0
- C \(\frac{1}{2}\)
- D 1
Answer & Solution
Correct Answer
(B) 0
Step-by-step Solution
Detailed explanation
\begin{aligned} &\text { Multiplying } C_{1} \text { by } p \text { and then doing }\\ &\begin{aligned} C_{1} & \rightarrow C_{1}+q C_{2}+r C_{3} \text { , we get } \\ \Delta &=\frac{1}{p}\left[\begin{array}{ccc} -p & \cos R & \cos Q \\ p \cos R & -1 & \cos P \\ p \cos Q & \cos…
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