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The Law of Sines: with triangle ABC, the angles are A, B, & C. The sides {a, b, & c} are opposite of the respective capital letter vertex.

a/sin(A) = b/sin(B) = c/sin(C). You know the angles A, B, C; and two sides (say a & b).

So side c = a*sin(C)/sin(A) = b*sin(C)/sin(B).

You could also use the Law of Cosines: c^2 = a^2 + b^2 - 2*a*b*cos(C)

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Does an Isosceles have two equal sides?

Yes. Isosceles triangles have two identical sides and angles. They are also longer than the third side.All triangles have three sides. Isosceles triangles have two sides of the same length.


How do you find values for the third side of a triangle?

Perimeter -2 known sides = 3rd side 180 -2 known angles = 3rd angle


What is the length of the third side of an equilateral triangle have?

The length of the third side of an equilateral triangle is the same as the lengths of both of the other two sides.


How do you tell if triangles are congruent or not?

If they have the same sides and same angles then they are congruent.Two triangles are called congruent if they have exactly the same size and shape. This can be determined by measuring all three sides of both triangles and measuring all three angles of both triangles.The rules of geometry also tell us that we don't have to do all these measurement. Triangles have certain properties that simplify the matter. As an example, the sum of the internal angles of a triangle is 180 degrees. Therefore if two angles are known, the third angle is also known. Another is when three sides form a triangle, they only do so in one way so the angles between the sides can be determined.There are specific rules for determining if two triangle are congruent:All three corresponding sides of both triangles are the same size.Two corresponding sides are the same length and the angle between them is the sameTwo corresponding angles are the same and the side between them is the same lengthTwo angles are the same and the corresponding non-included side are equal.


What is the measure of the vertex angle of an isosceles triangle if one of its base angles measures 75 and its congruent sides each measure 15 cm?

The length of the congruent sides is irrelevant. If one of the base angles is 75 deg, the two base angles sum to 150 degrees. Since the sum of all three angles is 180 degrees, the third angle, the vertex angle, must be 180 - 150 = 30 degrees.

Related Questions

What are the measures of all angles in a triangle if 2 sides equal the third side?

If two sides of a triangle are equal in length to the third side, then the triangle is equilateral, and all angles are 60 degrees.


What are the sides of a triangle?

There are 3 sides of a triangle and it has 3 interior angles that add up to 180 degreesThe sum of the lengths of the two shorter sides must be greater than the length of the third side.A triangle must have 3 sides, with angles that add to 180degrees. The sides can be any length.


The congruent sides of an isosceles triangle?

The congruent sides of an isosceles triangle are the two sides that are equal in length. These two sides are opposite the equal angles of the triangle. The third side, called the base, is not equal in length to the other two sides.


Does an Isosceles have two equal sides?

Yes. Isosceles triangles have two identical sides and angles. They are also longer than the third side.All triangles have three sides. Isosceles triangles have two sides of the same length.


How do you find values for the third side of a triangle?

Perimeter -2 known sides = 3rd side 180 -2 known angles = 3rd angle


What are the diff kinds of triangles?

One way of classifying triangles is by the number of congruent sides (angles). A triangle is equilateral if all its sides are equal. All its angles will also be equal. A triangle is isosceles if two of its sides are equal. The angles at the end of the third side will be equal to one another. A triangle is scalene if all three sides are of different length. In this case, all three angles will also be different.


How many different crystals are crystals classified into?

Seven. They are: Cubic - all angles 90 degrees, all sides equal length Trigonal - all angles 90 degrees, two sides equal and the third unequal Orthorhombic - all angles 90 degrees, no sides equal Hexagonal - two angles 90 degrees and one angle 120 degrees, two sides unequal and the third unequal Trigonal - all angles equal but not 90, all sides equal Monoclinic - two angles 90, one more than 90, and no sides equal Triclinic - no angles equal, no sides equal For a graphical representation of these, see http://en.wikipedia.org/wiki/Crystal_system#Classification_of_lattices


What is the meaning of Side angle side Congruence?

It means that if two triangles have two sides with the lengths of the corresponding sides that are equal (congruent) and the angles between between the two sides congruent, then the triangles are congruent (i.e., the three corresponding lengths of sides and three corresponding angles are all congruent). For example, if you know that triangle one has sides of length 1 and 2 and the angle between the two sides is 60 degrees and that triangle two has sides of length 1 and 2 and the angle between the two sides is 60 degrees, this theorem says that the triangles are congruent, so the length of third side of both triangles is the same and the measure of the other two angles in triangle one is the ame as the measure of the other two angles in triangle two.


What relationships exist between the two congruent sides of an isosceles triangle and its base?

The angles where the equal sides meet the third side of the triangle are equal angles.


What kind of triangle has two sides with length 15 and one side with length 25?

isoscelesAs regard their sides, triangles may beScaleneIsoscelesEquilateralAnd in regard to their angles, triangles may beAcuteRightObtuseEquiangularA triangle is scalene if all of its three sides are 'different'.If only two of its sides are equal, the triangle is called isosceles.A triangle with all three 'equal' sides is called equilateral.So, a triangle with a length of 15 on two sides and a length of 25 on the third side would be Isosceles, since two of the sides are the same.


What is the measure of the third side of an equiteral triangle have?

The length of the third side is the same as the length of either of the other two sides.


How many of the interior angles in an isosceles triangle have the same number of degrees?

In an isosceles triangle, two of the interior angles have the same number of degrees. This is because an isosceles triangle has two sides of equal length, which means the two base angles (the angles opposite those equal sides) are congruent. The third angle, called the apex angle, can be different from the base angles unless the triangle is also equilateral.