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You have a triangle with an angle of 80 degrees and the opposite side being 2 cm. You also have an adjacent side that's 4 cm long. Those sides and the angle specified make for an impossible situation. Let's prove that using the law of sines.
The law of sines states that in a triangle, the ratio of the sine of an angle to the length of the opposite side is a constant within that triangle. So
sin(A)/a = sin(B)/b = sin(C)/c
Let's just deal with those sides and angles involving A and B.
sin(A)/a = sin(B)/b
Now substitute the known values
sin(80)/2 = sin(B)/4
0.984807753/2 = sin(B)/4
0.492403877 = sin(B)/4
4*0.492403877 = 4*sin(B)/4
1.969615506 = sin(B)
And we now have an impossible situation since the sine of an angle has to be in the range -1 to 1 and the value 1.969615506 is obviously well beyond that range. Therefore there are no triangles with that angle and side lengths.
