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Mathematics 18 Online
OpenStudy (anonymous):

Which of the following statements is/are true? (1) In an isosceles triangle, the incentre, the circumcentre, the centroid and the orthocentre lie in a straight line. (2) In an equilateral triangle, the incentre, the centroid and the circumcentre are one and the same point. (3) The centroid and the orthocenter of a triangle always lie inside a triangle. (4) Only in an acute angled triangle, the incentre lies inside the triangle.

OpenStudy (ikram002p):

lol lets see them one but one hehe

OpenStudy (ikram002p):

by*

ganeshie8 (ganeshie8):

we can eliminate option (3) i guess http://www.mathopenref.com/triangleorthocenter.html

ganeshie8 (ganeshie8):

need to work rest of the options

OpenStudy (ikram002p):

okkkk ill see 1 :P

OpenStudy (anonymous):

OpenStudy (anonymous):

4th one is also not the option

OpenStudy (ikram002p):

mmmm |dw:1405323817874:dw|

OpenStudy (ikram002p):

ok its always 2 lol

ganeshie8 (ganeshie8):

(1) is true ? yes we can eliminate (3) and (4) safely

OpenStudy (ikram002p):

1 is not always true

OpenStudy (anonymous):

The orthocenter, the centroid and the circumcenter of a non-equilateral triangle are aligned; that is to say, they belong to the same straight line, called line of Euler.

OpenStudy (ikram002p):

mmm then it should be true for isosceles triangle ? nice !

OpenStudy (anonymous):

so it is isosceles

ganeshie8 (ganeshie8):

Euler again xD

OpenStudy (ikram002p):

ok so we need to check if incentre on the same line as well

OpenStudy (anonymous):

yes

OpenStudy (anonymous):

yes it also incentre option 1 is correct

OpenStudy (anonymous):

In an acute triangle, the 4 centers are all inside the triangle:

OpenStudy (ikram002p):

how did u got incentre on the same line ?

OpenStudy (anonymous):

so 4 is also correct

OpenStudy (ikram002p):

4 is wrong lol

OpenStudy (anonymous):

In an isosceles triangle, the 4 centers are collinear. This is true because in an isosceles triangle, the altitude to the base is also a median and an angle bisector. This line is the one line of reflection symmetry for the triangle

OpenStudy (ikram002p):

nice !

OpenStudy (anonymous):

OpenStudy (ikram002p):

not colinear ?

OpenStudy (anonymous):

its lie inside the triangle

OpenStudy (ikram002p):

?

OpenStudy (anonymous):

acute angle .see the th option they asked for whether its lie inside the acute triangle

OpenStudy (ikram002p):

(4) Only in an acute angled triangle, the incentre lies inside the triangle. its wrong since it says "Only" , the incentre lies inside the triangle all the time no matter what angle was

OpenStudy (anonymous):

yes u are right!i didnt see only

OpenStudy (ikram002p):

^^

OpenStudy (anonymous):

2 is also the right option

OpenStudy (anonymous):

In an equilateral triangle, all centers are the same point. This is because the altitude to each side of an equilateral triangle is also a median and an angle bisector. The equilateral triangle is the most symmetrical triangle of all, and has 3 lines of reflection symmetry (those same altitudes). The equilateral triangle has 120 degree rotation symmetry about the "center" (Orthocenter, Centroid, Circumcenter, and Incenter). The equilateral triangle is the only triangle that does have rotation symmetry.

OpenStudy (anonymous):

so 1 and 2

OpenStudy (ikram002p):

well lol as u say , but me dint convince yet mmm ill check it by my own ^_^

OpenStudy (anonymous):

k .i will show you the image

OpenStudy (ikram002p):

not sure about 2 but 1 is correct

OpenStudy (anonymous):

OpenStudy (ikram002p):

well what if it was obtuse triangle ? mmm

OpenStudy (anonymous):

In an obtuse triangle, the Circumcenter and Orthocenter are outside the triangle, while the other 2 centers are inside the triangle.

OpenStudy (ikram002p):

this is equvilant im not sure about 2 not 1

OpenStudy (ikram002p):

wait im not sure about 1 2 is correct *sigh* can't focus with u lol

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