I think it should be 1.7?
a^2 + b^2 = c^2
c^2 = 16
Square root of 16 is 4.
1 + 3 = 4
Square root of 1 is 1 and square root of 3 is given, which is 1.7.
An equilateral has two right triangles out together, so basically that would be a rectangle.
1 x 1.7 = 1.7