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Three Dimensional Geometry — Maths STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 ScienceMathsThree Dimensional Geometry1 Mark
MCQ
Area of $\triangle\text{ABC}$ is:
  • A
    45 squares units
  • B
    55 squares units
  • C
    65 squares units
  • D
    none of these
✓

Answer

  1. none of these

Solution:

Line PA: $\frac{\text{x}-1}{1}=\frac{\text{y}-2}{-1}=\frac{\text{z}-6}{1}$

Line PB: $\frac{\text{x}-1}{-1}=\frac{\text{y}-2}{2}=\frac{\text{z}-6}{1}$

Line PC: $\frac{\text{x}-1}{2}=\frac{\text{y}-2}{-1}=\frac{\text{z}-6}{-2}$

Then $\text{A}\Big(\frac{7}{2},-\frac{1}{2},\frac{17}{2}\Big)$

$\text{B}\Big(\frac{17}{2},-13,-\frac{3}{2}\Big)$

$\text{C}\Big(-14,\frac{19}{2},21\Big)$

Hence area of $\triangle\text{ABC}=\frac{225\sqrt{14}}{8},$ volume of tetrahedron

$\text{PABC}=\frac{125}{8}\text{cubic units}$

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