Mark M. answered 03/03/19
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
The 3rd degree Taylor Polynomial is:
f(π/4) + f'(π/4)(x - π/4) + [f"(π/4) / 2!](x-π/4)2 + [f'''(π/4) / 3!]( x - π/4)3
f(x) = sin(2x), so f(π/4) = sin(π/2) = 1
f'(x) = 2cos(2x), so f'(π/4) = 0
f"(x) = -4sin(2x), so f"(π/4) = -4
f'''(x) = -8cos(2x), so f'''(π/4) = 0
Taylor Polynomial: 1 - 2(x - π/4)2