two side of triangle is 15 cm each. subtrend of triangle is 60 degree find the other side?

Answer 1

It doesn't matter which angle is specified as 60 degrees. because you are told that two sides are 15cm, then you have an isosceles triangle where at least 2 sides are the same. If 60 is the angle between the two sides, then the other two must be equal and add to 120 (since all angles in a triangle add to 180). But since they are equal, they must each be 60 degrees.

Or if you are told that one of the other angles is 60, you know from an isosceles triangle that the other is 60. That forces the 3rd angle to be 60 also.

If all the angles are equal, then the sides must also be equal because you have an *equilateral* triangle, so the third side must also be 15 cm.

Answer 2

A triangle with two sides of equal length is considered isosceles. Your triangle is also isosceles because it has two sides of 15 cm each. An isosceles triangle has a special property: the angles opposite the sides with equal length are congruent (of equal measure). Since the subtrend angle is 60 degrees, the remaining angles have to add up to 120 degrees (the sum of the angles of a triangle are 180 degrees). Because the two angles are congruent, they are also 60 degrees each. In fact, no matter which angle you start your calculation, the only possibility is 60 degrees for each angle with your given lengths. This means your triangle is not just isosceles, it is also equilateral. It has all equal angles and equal sides. Therefore, the length of the third side is also 15 cm. I hope this helps. Good luck!

Answer 3

I'll assume 60 deg is between the two given legs:
L = 2(15) sin(30) = 15 cm , you have a quadrilateral triangle