how do I work our angles when only have dimensions of triange?
sides of triangle 7.5, 19.5, 18 is a right angled traingle?
You can solve this by using the sine or cosine of the angles.
You obtain those by dividing the length of one side of the
triangle by the length of the hypotenuse, which must be the
longest of the three sides.
First angle:
7.5 / 19.5 = 0.38461
Using the inverse sine function, you find the angle is 22.619 degrees.
Second angle:
18 / 19.5 = 0.92307
Using the inverse sine function again, the angle is 67.380 degrees.
Adding those two angles, taking into account the rounding errors,
you get 90 degrees. The sum of all three angles in any triangle
is 180, so the third angle must be 90 degrees. That makes this
a right triangle.