Determine what kind of triangle is formed with the given lengths: 2.8, 5, 2.8.?

Question

Here are the answer choices:

A) equilateral
B) right
C) acute
D) scalene
E) obtuse

When you answer it, can you tell me how you did it? Please? thanks.

Answer 1

Use the Law of Cosines to get the three angles; then you can answer the question.

c² = a² + b² + 2 a b cos ( angle between a and b )

Answer 2

Trig was a while ago (1986?), but I've been teaching 3rd - 5th grades for 12 years and math is fun. So.... The obvious answer is an isosceles triangle, but that is not an option.

-Two of the sides are the same length.
-Both sides shorter than the hypotenuse, just over 1/2 its length.

There is a direct relationship between the relative length of sides and their opposite angles. The greater the relative length (compared to the other two sides) the greater its opposite angle.

Walk with me here.

If all three sides were 5" in length their angles would be the same: 60 degrees. (a triangle has 180 degrees)

Since the hypotenuse is 5" in length and the other two sides are just over 1/2 its length each (2.8"), their opposite angles would be quite small (acute). If they were much smaller, say 2.5", they wouldn't be able form a triangle, rather, they would just meet and form on line on top of the hypotenuse.

Your triangle as two very acute angles that are less than 30 degrees each and one obtuse angle that is quite a bit greater than ninety degrees.

It is an obtuse triangle.

Thanks for the challenge. Do I get the credit?

Answer 3

its not an equilateral triangle as all the 3 sides are not equal

its not a right triangle either as pythogoras theorem cant be applied here (2.8^2 +2.8^2 =15.68 and not 5^2)

its not a scalene triangle as 2 sides are equal


its an isoscles triangle . but as thats not an answer option , its either an acute or obtuse triangle

Answer 4

answer is E)obtuse
obtuse triangle means one of the angles is more than 90°

using law of cosines, we can prove than the angle opposite the 5 (unit) side is more than 90°

c² = a² + b² - 2abcosθ
5² = 2.8² + 2.8² - 2(2.8)(2.8)cosθ
arccos[(5² - 2.8² - 2.8²)/(2*2.8*2.8)] = θ
θ = 126.47°

Answer 5

E
if you use cosine law
a^2=b^2+c^2-2bccosa
you will find that the triangle is a 26.8,26.8 and 126.5 degree triangle , this is obtuse triangle

Answer 6

E = Obtuse ...... really old school would have called this NOT a tri-oscelese triangle

Answer 7

Isosceles

Answer 8

properly in my quantum mechanics type linear version is very tuff. Im specific you ought to locate quite some the equations on google in case you typed: linear version equation quantum mechanics...or something like that.