Is it true that an isosceles triangle must have only two equal angles?

Question

I need this answer as soon as possible, thanks. You just need to write "true" or "false" in your answer to my question, but a detailed explanation will be appreciated too..

Answer 1

yes it is true.

It must have two equal sidesss and one different if they were all the same it would be an equilateral triangle

Answer 2

Contrary to several answerers, an isosceles triangle is really defined to be:

An isosceles triangle is a triangle with (at least) two equal sides. [See source.]

It is the equal sides characteristic that defines the isosceles triangle, not two equal angles. True, we can show that, if there are two equal sides, there must also be two equal angles. But the definition is about the sides, not the angles.

By the way, the cited source also says that an equilateral triangle is just a "special case" of the isosceles.

PS: "iso" as a prefix means "equal", not "two" as one answerer put it. Thus, an ISObar, for example, is a place where the atm pressure (bar) is equal (iso). Isobars are those squiggly lines you can see on a weather map. At each point on the same line, the atm pressures are equal to each other.

Answer 3

A triangle with two congruent angles (two angles that are the same size) is an isosceles triangle. An isosceles triangle also has two congruent legs (two sides of the same length). For three sides to form a triangle, the two shortest sides must sum to a number larger than the longest side. I'm not exactly sure what you are asking but this is what I got from your question. Hope I helped, Jade <3 P.S. If you need more help, just contact me somehow.

Answer 4

True. If one states that an equilateral triangle is a special case of an isosceles triangle because at least two of it's sides are equal, then your stating that an equilateral triangle is always an isosceles triangle. When you state that an isosceles triangle is not limited to two equal sides then you are stating that an isosceles triangle is also always an equilateral triangle. In plainer words, an isosceles triangle is the same as an equilateral triangle and an equilateral triangle is the same as an isosceles triangle and there is no difference between them. This is what the comments on this board have spelled out.
There are three types of triangles in plane geometry. They are entirely distinct from one another, in a specific and definable way, and none of them are subsets or 'special cases' of each other.
There is a type of triangle that has three equal sides which has been given the name equilateral. The name means equal sided.
Then there is a type of triangle which has two equal sides only, with the third unequal side called the base. The name given to this type of triangle is isosceles. The name means, literally, equal legged, and refers to the two equal sides or legs above the base, imagine two legs standing on the ground.
The last type of triangle has three unequal sides and has been given the name of scalene from the Latin scalenus which means unequal.
There are ONLY three types of triangles: one with three unequal sides( which means no equal sides), one with three equal sides, and one with two equal sides. The phrases " at least two equal sides" or" not limited to two equal sides" used in some answers here are nonsense.

Answer 5

False. An isosceles triangle is a triangle with (at least) two equal sides. An equilateral triangle is a special case of an isosceles triangle having not just two, but all three sides and angles equal.

Answer 6

False.

By definition, an isosceles triangle is a triangle with (at least) two equal sides and thus (at least) two equal angles.

An equilateral triangle is therefore a special case of an isosceles triangle having not just two, but all three sides and angles equal.

It follows the same idea that by definition a square is a type of rectangle, but a rectangle is not necessarily a square.

Answer 7

Arsenal and Dr. Nightcall both refer to the same web site but come to opposite conclusions. An equilateral triangle is a special case of an isosceles triangle, so an isosceles triangle must have at least two angles equal, but may also have three. Dr. Nightcall is correct.

Answer 8

True. This is the definition of an isoceles triangle. Two sides are equal and thus two angles (opposite the equal sides) are also equal. Now here is the new wave technical answer. If you wish to stretch the definition of an isoceles triangle as being a triangle with two sides equal and not making any reference to the third side also being equal, you could end up stating that equilateral triangles are also isosceles - I don't go for that new wave thinking, but some do just to confuse students. Perhaps it helps in stretching the thinking outside the box (triangle?).

Answer 9

an isosceles triangle has 2 equal angles, or 2 equal sides.
that does not exclude the posibility having all 3 sides or angles equal (even though those triangles have a different name)

Answer 10

It is true. An isosceles triangle has two equal angles and an equilateral triangle has all angles equal.

Answer 11

The definition of an isosceles triangle is a triangle that has two or more equal angles, and therefore, two or more sides of equal length.