3 and 4 .Determinants and Matrices
easy

एक त्रिभुज का क्षेत्रफल ज्ञात कीजिए जिसके शीर्ष $(3,8),(-4,2)$ और $(5,1)$ हैं।

A

$\frac {61}{2}$

B

$\frac {65}{2}$

C

$\frac {71}{2}$

D

$\frac {33}{2}$

Solution

The area of triangle is given by

$\Delta  = \frac{1}{2}\left| {\begin{array}{*{20}{r}}
  3&8&1 \\ 
  { – 4}&2&1 \\ 
  5&1&1 
\end{array}} \right|$

$ = \frac{1}{2}[3(2 – 1) – 8( – 4 – 5) + 1( – 4 – 10)]$

$ = \frac{1}{2}(3 + 72 – 14) = \frac{{61}}{2}$

Standard 12
Mathematics

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