Question

find the area of triangle with vertical(-1,5),(3,1),(5,7​

Answer 1

Area of triangle=

2

1

(x

1

(y

2

−y

3

)+x

2

(y

3

−y

1

)+x

3

(y

1

−y

2

)) where x=1,x

2

=3,x

3

=5, y

1

=2,y

2

=7,y

3

=3

⇒

2

1

(1(7−3)+3(3−2)+5(2−7))

⇒

2

1

(1−(4)+3(1)+5(−5))

⇒

2

1

(4+3+(−25)

=

2

1

(−25+7)

=

2

1

(−18)

Area of triangle =9cm.

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