cos(x) = ³/₅
cos⁻¹[cos(x)] = cos⁻¹(³/₅)
x ≈ 53.13
sin(2x) = sin[2(53.13)]
sin(2x) = sin(106.26)
sin(2x) = 0.960001
cos(2x) = cos[2(53.13)]
cos(2x) = cos(106.26)
cos(2x) = -0.27999657
tan(2x) = tan[2(53.13)]
tan(2x) = tan(106.26)
tan(2x) = -3.428617001
