Get Answers to all your Questions

header-bg qa

Need Solution for R.D.Sharma Maths Class 12 Chapter 25 Scalar Triple Product  Exercise 25.1 Question 10 Maths Textbook Solution.

Answers (1)

Answer:\left ( \vec{a}-\vec{b} \right ).\left \{ \left ( \vec{b}-\vec{c} \right )\times \left ( \vec{c}-\vec{a} \right ) \right \}=0

Hint :- Use cross-product to prove

Given:\left ( \vec{a}-\vec{b} \right ).\left \{ \left ( \vec{b}-\vec{c} \right )\times \left ( \vec{c}-\vec{a} \right ) \right \}=0

\begin{aligned} \text { L.H.S } &=\left(\vec{a}_{-} \vec{b}\right) \cdot\{(\vec{b}-\vec{c}) \times(\vec{c}-\vec{a})\} \\ &=(\vec{a}-\vec{b}) \cdot\{\vec{b} \times(\vec{c}-\vec{a})-\vec{c} \times(\vec{c}-\vec{a})\} \\ \end{aligned}

              \begin{aligned} &=(\vec{a}-\vec{b}) \cdot((\vec{b} \times \vec{c})-(\vec{b} \times \vec{a})-(\vec{c} \times \vec{c})+(\vec{c} \times \vec{a})) \: \: \: \quad(\because \text { Distributive law }) \\ \end{aligned}

              \begin{aligned} &=(\vec{a}-\vec{b}) \cdot((\vec{b} \times \vec{c})-(\vec{b} \times \vec{a})-0+(\vec{c} \times \vec{a})) \quad(\because \vec{c} \times \vec{c}=0) \\\\ &=(\vec{a}-\vec{b}) \cdot((\vec{b} \times \vec{c})+(\vec{a} \times \vec{b})+(\vec{c} \times \vec{a})) \quad(\vec{a}) \\\\ &=\vec{a} \cdot(\vec{b} \times \vec{c})+\vec{a} \cdot(\vec{a} \times \vec{b})+\vec{a} \cdot(\vec{c} \times \vec{a})-\vec{b} \cdot(\vec{b} \times \vec{c})-\vec{b} \cdot(\vec{a} \times \vec{b})-\vec{b} \cdot(\vec{c} \times \vec{a}) \\\\ &=\left[\begin{array}{ll} \vec{a} \vec{b} & \vec{c}]+0+0-0-0-[\vec{a} \vec{b} \vec{c}] \end{array}\right.\\\\ &=0 \\ &=\mathrm{R} . \mathrm{H} . \mathrm{S} \text { (Hence proved) } \end{aligned}

Posted by

infoexpert21

View full answer

Crack CUET with india's "Best Teachers"

  • HD Video Lectures
  • Unlimited Mock Tests
  • Faculty Support
cuet_ads