Orthocenter that a Triangle(Definition, how to Find, Video, & Examples)

The orthocenter of a triangle, or the intersection that the triangle"s altitudes, is no something that comes increase in casual conversation. Managing orthocenters, it is in on high alert, due to the fact that we"re handling coordinate graphing, algebra, and geometry, all tied together. It is anything however casual mathematics.

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How to uncover the Orthocenter that a Triangle

Triangles and Their Parts

A triangle, the simplest polygon with only three right line segments creating its sides, has several exciting parts:

Sides -- 3 sides intersecting in ~ vertices, creating three inner anglesAltitudes -- The heat segment from each vertex that the triangle come the opposite next (or extension of the opposite side) that is perpendicular to the opposite side. Since the segment native the inner angle to the opposite next is perpendicular, one altitude that a triangle will always type a right angle v the next to which the is perpendicular.Orthocenter -- The intersection that the three altitudes.

It doesn"t matter if you are managing an Acute triangle, Obtuse triangle, or a ideal triangle, all of these have actually sides, altitudes, and also an orthocenter. In addition to the orthocenter, there are three other varieties of triangle centers:

Incenter - The incenter the a triangle is situated where all 3 angle bisectors intersect.Circumcenter - The circumcenter is situated at the intersection that the perpendicular bisectors of all sides. This will take place inside acute triangles, external obtuse triangles, and for right triangles, it will occur at the midpoint that the hypotenuse.Centroid - The centroid, or a triangle"s center of heaviness point, is located where all 3 medians intersect.Orthocenter - The orthocenter lies at the intersection of the altitudes.

All four of the centers above occur in ~ the same point for an it is intended triangle. One more interesting truth is the the orthocenter, centroid, and also circumcenter of any type of triangle are collinear. These 3 points will always lie top top the exact same straight line, i m sorry is called the Euler line. The Euler heat is named after it"s discoverer, Leonhard Euler.

What is the Orthocenter the a Triangle?

The orthocenter of a triangle is the allude of intersection of any type of two of three altitudes that a triangle (the third altitude have to intersect at the same spot).


You can uncover where two altitudes of a triangle intersect utilizing these 4 steps:

Find the equations of 2 line segments forming sides of the triangleFind the slopes of the altitudes for those two sidesUse the slopes and also the the contrary vertices to find the equations that the two altitudesSolve the corresponding x and also y values, offering you the collaborates of the orthocenter

Those may sound like four easy steps, however embedded within them is the expertise to uncover two equations:

The equation that a lineThe equation that a perpendicular line

How to discover the Orthocenter that a Triangle

Here we have actually a coordinate grid with a triangle snapped to network points:


Point M is at x and also y collaborates (1, 3)

Point R is at (3, 9)

Point E is in ~ (10, 2)

Step One

Find the equations of lines developing sides MR and also RE. You do this v the formula y = mx + b, wherein m is the steep of the line, and also b is the y-intercept.

To uncover the steep of heat MR, you plugin the works with as the change in y values over the adjust in x values:

For ours triangle"s side MR, it looks prefer this:

m = (9 - 3)(3 - 1)

m = 62

m = 3

Return to your equation and also plug in 3 because that m:

y = 3x + b

You currently have x and also y values, so usage either given suggest and plugin its numbers. Use suggest M, because that example:

3 = 3(1) + b

3 = 3 + b

0 = b

You can test this by using suggest R (it will offer the same answer):

9 = 3(3) + b

9 = 9 + b

0 = b

So for line segment grandfather the equation that the line is y = 3x. Repeat these because that line segment RE:

slope (m) = (y2 - y1)(x2 - x1)

m = (2 - 9)(10 - 3)

m = -77

m = -1

Now let"s plugin -1 right into our equation:

y = mx +b

y = -1x +b

Use suggest R again:

9 = -1(3) + b

9 = -3 + b

12 = b

The equation that the line segment RE is y = -1(x) + 12

That was all simply step one!

Step Two

For step two, uncover the slopes the perpendiculars come those given sides. You need the steep of each line segment:

For MR, m = 3

For RE, m = -1

To discover the slope of a heat perpendicular to a provided line, you require its negative reciprocal:


For MR, -13

For RE, -1-1 = 1

Step Three

For action three, usage these new slopes and the works with of the opposite vertices to discover the equations the lines that type two altitudes:


For next MR, the altitude is AE, v vertex E in ~ (10, 2), and also m = -13:

y = mx + b

2 = (-13) 10 + b

2 = -103 + b

2 + 103 = b

163 = b

The equation for altitude AE is y = -13 x + 163.

For side RE, the altitude is VM, with vertex M at (1, 3), and m = 1:

y = mx + b

3 = 1(1) + b

3 = 1 + b

2 = b

The equation for altitude VM is y = x + 2.

Step Four

You have the right to solve for 2 perpendicular lines, which method their x and y coordinates will intersect:

y = (-13) x + 163

y = x + 2

Solve because that each coordinate; very first for x:

(-13) x + 163 = x + 2

x = 2.5

Solve because that y, utilizing either equation and plugging in the uncovered x:

y = -13 (2.5) + 163

y = 4.5


Test it with the other equation:

y = 2.5 + 2

y = 4.5

The orthocenter that the triangle is at (2.5, 4.5). Whew! four (long) but an useful steps.

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Orthic Triangle and also the Circumcircle

Working through these examples, you may have actually noticed a smaller triangle is developed by the feet of the 3 altitudes. This smaller triangle is called the orthic triangle. There are countless interesting nature of the orthic triangle because that you to discover, such together the circumcircle the the orthic triangle, likewise called the nine-point-circle of a triangle.

Next Lesson:

Triangle Inequality Theorem

Lessons Summary:

After working your means through this lesson and also video, you will be maybe to:

Find the name: coordinates points that a triangle"s orthocenterExplain the 4 steps essential to find the coordinate points that a triangle"s orthocenter