if you have 2 sides of a triangle measured how do you get the the 3rd???

Answer 1

If it's a right triangle (one of the angles is 90 degrees) you can use the pythagorean theroem:
a^2 + b^2 = c^2
Where a and b are the two legs and c is the hypotenuse (the side opposite the 90 degree angle). Just plug in your numbers and solve for the third!

If it's not a right triangle and you have one of the angles in addition to the two sides, you can use the law of cosines:
c^2 = a^2 + b^2 + 2ab*cos(C)
Where c is the side of the triangle you are looking for, a and b are the sides you know, and C is the angle you know.

hope that helps!

Answer 2

You have to have at least one angle. If the angle is
between the sides then use the law of cosines.

sides a, b,c and angle C opposite side c with a,b and angle C known

a^2 + b^2 = c^2 + 2abcosC........Notice that if C is a rt. angle
then since cos(π/2)=0 the cosine law is simply the
Pythagorean Theorem.


But if the angle is off the end of one of the sides then
you must start with the law of the sines.

Suppose the known angle A is opposite known side a and
side b is known.

a/sinA = b/sinB Now you can solve for angle B
then 180-A-B=C and back to the law of cosines to solve for
side c.
....And notice that if angle A is a rt. angle that
sinB=b/a the simple trig function. Then c=b/tanB.

Answer 3

Are you talking about the right triangle or just any triangle?

If you are limiting yourself to right triangles (one containing 90 degree angle) then you can use this formula

a^2 = b^2 + c^2
(b is the hypotenuse)

If you are NOT limiting yourself to right triangles, then the formula becomes
a^2 = b^2 + c^2 - 2bcCOS(A)

It is called the law of cosine.

Answer 4

You will not get the exact lenghth of the 3rd side, just the range of its values.

if you have 2 and 1 as the 1st and 2nd sides respectively,just use this with x as the 3rd side

2-1 1

Answer 5

What kind of triangle is it? is it a right triangle or not? If right, then a^2 + b^2 = c^2

Answer 6

If it is a right triangle, meaning one of the sides is 90 degrees, then you can use the pythagorean theorem. If it isn't you can use trigonometry to figure out the last side using cosine, sine, or tangent properties.

Answer 7

if it is a right triangle. a^2 + b^2 = c^2. c is the longest side or the hypotenuse and a and b are the legs.

Answer 8

well a measure of a triangle has to be 180 add the 2 and subtract them from 180 if not use the pathagreum theorum

Answer 9

if you talk about a scalen triangle then the third side must be more than the difference of the first and second and less than the sum of the first and second

Answer 10

if its a right triangle, then
a^2 + b^2 = c^2

if it is not a right triangle then

Law of Cosines
a^2 = b^2 + c^2 - 2bc(cos(A))
b^2 = a^2 + c^2 - 2bc(cos(B))
c^2 = a^2 + b^2 - 2bc(cos(C))

Law of Sines
a/sin(A) = b/sin(B) = c/sin(C)

Law of Tangents
(a - b)/(a + b) = (tan((A - B)/2))/(tan((A + B)/2))

However with those 3 laws, you will need some angles.