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Re: Everything About Triangles For GMAT. [#permalink]
24 Nov 2009, 09:49

awesome guide thanks! so there are other guides like this? I'm taking the GMAT tomorrow, I would love to have a quick but thorough review. can someone post the other guides? Thanks

Re: Everything About Triangles For GMAT. [#permalink]
24 Nov 2009, 10:06

manifestdestiny wrote:

awesome guide thanks! so there are other guides like this? I'm taking the GMAT tomorrow, I would love to have a quick but thorough review. can someone post the other guides? Thanks

Check out sticky threads in Math and Verbal forums. Pretty much everything important is collected up there.

Re: Math: Triangles [#permalink]
27 Dec 2009, 06:04

Expert's post

logan wrote:

Exceptional... a really well compiled data on triangles and their properties... the best part was to mention the problems from the official GMAT books.... +2

i think it would be worth mentioning the sine and cosine rules of triangles...

The law of sines (or Sine Rule):

If A, B and C are the angles made by the sides a= BC, b= CA & c= AB at the vertices of a triangle ABC, then according to the sine rule, (a/sin A) = (b/sin B) = (c/sin C)

The law of sines can be used to compute the remaining sides of a triangle when two angles and a side are known.

The law of cosines (or Cosine Rule) :

If A, B and C are the angles made by the sides a= BC, b= CA & c= AB at the vertices of a triangle ABC, then according to the cosine rule,

The law of cosines is useful for computing the third side of a triangle when two sides and their enclosed angle are known, and in computing the angles of a triangle if all three sides are known.

I withdrawn these rules as well as some other properties and formulas (there are plenty of them), as GMAT problems doesn't require knowing them for solving. No GMAT guide (as I know) mentions them in quant section. _________________

Re: Math: Triangles [#permalink]
14 Jan 2010, 15:34

A masterpiece Bunuel . Amazing summary of triangle proprties. Some Questions to have more clarity .

Are the medians equal in length in a scalene traingle ?

Does the centroid neccasarily have to be a center of circumcircle of a scalene triangle or in other words, does it mean that each triangle can be circumcircled ?

Re: Math: Triangles [#permalink]
14 Jan 2010, 16:01

Quote:

The SSA condition proves congruence if the angle is obtuse or right. In the case of the right angle (also known as the HL (Hypotenuse-Leg) condition or the RHS (Right-angle-Hypotenuse-Side) condition), we can calculate the third side and fall back on SSS.

Re: Math: Triangles [#permalink]
14 Jan 2010, 16:47

Expert's post

GMATMadeeasy wrote:

A masterpiece Bunuel . Amazing summary of triangle proprties. Some Questions to have more clarity .

Are the medians equal in length in a scalene traingle ?

Does the centroid neccasarily have to be a center of circumcircle of a scalene triangle or in other words, does it mean that each triangle can be circumcircled ?

Generally medians are not equal, so in scalene triangle medians are not equal.

Centroid is not the center of the circumscribed circle. (There was a typo in the text, edited.)

As for the circumscribed triangles: yes, any triangle can be circumscribed. _________________

Re: Math: Triangles [#permalink]
14 Mar 2010, 01:20

Bunuel, First of all thank you for the excellent compilation. I am using MGMAT books. And on this page I found many triangle concepts not covered in the book. Scary actually.

I wud like to know from other knowledgeable members, what they think about MGMAT books in terms of coverage of concepts?

Re: Math: Triangles [#permalink]
17 Jun 2010, 11:06

Quote:

Usually called "half of base times height", the area of a triangle is given by the formula below. • A=\frac{hb}{2}

Other formula: • A=\frac{P*r}{2}

• A=\frac{abc}{4R}

Where b is the length of the base, a and c the other sides; h is the length of the corresponding altitude; R is the Radius of circumscribed circle; r is the radius of inscribed circle; P is the perimeter

Just to clarify, is P the perimeter of the circle or the triangle?

Quote:

• For an isosceles triangle with given length of equal sides right triangle (included angle) has the largest area.

Will u elaborate on this please? I'm not sure how this works.

Thanks a lot of the summary, very complete and succinct! :D

gmatclubot

Re: Math: Triangles
[#permalink]
17 Jun 2010, 11:06

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