It is generally useful to use the formula. The procedure is to substitute the given values for the variables in the formula, then do the arithmetic.
... A = (1/2)r²·θ . . . . r is the radius, θ is the central angle in radians
Put the numbers in ...
... A = (1/2)(4 in)²·(π/3)
... A = 8π/3 in² ≈ 8.37758 in²