Question Details

The vertices of a triangle ABC are A(1, 2), B(–3, 4), C(5, 8), then orthocentre of △ABC is

Options

A

(2/3, 1)

B

( -7/3, 2)

C

(2, 3)

D

(3/2, 1)

Show Answer

Correct Answer :

Option D

(3/2, 1)

Solution :

The correct option is (3/2, 1).

To find the orthocenter of the triangle ABC with vertices A(1,2), B(-3,4), and C(5,8), we need to determine the intersection point of the altitudes of the triangle.

Step 1: Find the equation of the altitude from vertex A to side BC.
First, we find the slope of side BC. The vertices are B(-3,4) and C(5,8).
mBC=8-45-(-3)=48=12
Since the altitude from A (let's call it AD) is perpendicular to BC, the slope of AD (m1) is:
m1=-1mBC=-2
Now, using the point-slope form for the line passing through A(1,2) with slope -2:
y-2=-2(x-1)
y-2=-2x+2
2x+y=4 --- (Equation 1)

Step 2: Find the equation of the altitude from vertex B to side AC.
First, we find the slope of side AC. The vertices are A(1,2) and C(5,8).
mAC=8-25-1=64=32
Since the altitude from B (let's call it BE) is perpendicular to AC, the slope of BE (m2) is:
m2=-1mAC=-23
Using the point-slope form for the line passing through B(-3,4) with slope -23:
y-4=-23(x-(-3))
3(y-4)=-2(x+3)
3y-12=-2x-6
2x+3y=6 --- (Equation 2)

Step 3: Solve Equation 1 and Equation 2 simultaneously to find the orthocenter.
From Equation 1, we have:
y=4-2x
Substitute this value of y into Equation 2:
2x+3(4-2x)=6
2x+12-6x=6
-4x=6-12
-4x=-6
x=-6-4=32
Now substitute x=32 back to find y:
y=4-2(32)=4-3=1

Therefore, the orthocenter of the triangle is (32,1).

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