Solve
sin 2 theta = 0.8

In this question it is actually necessary to find the value of theta. there are several methods by which the value of theta can be determined. One of the procedures is described below. As per my understanding, this is the easiest procedure.
sin2 theta = 0.8
Dividing both sides by sin we get the equation in a new format.
2 theta = sin⁻¹ 0.8
2 theta = 53.13
theta = 53.13/2
         = 26.565
         = 26.6
So the value of theta is 26.6 degree. Hopefully this will make the problem clear to you and it is the easiest method as per my judgement.

Okay so for every triangle has three angles that always add up to 180 degrees. and to tell the difference between whether they are secure, right or obtuse is that acute: has one angle that is less than 90 degrees. right triangle means there is at least one angle that is exactly 90 degrees. and an obtuse angle has an angle that is bigger than 180 degrees. i’ll do #13 as an example: 13. 40 and 50 so if every triangle has 180 degrees 40+50= 90 degrees then180-90= 90 degrees so the third angle is 90 degrees and because this triangle has a 90 degree angle it means it is a right triangle