Please help me with this

According the Chain Rule, the derivative of f(:r) : sin(6:r:) is d . 39:51:1(63): 6005(6x) V d' . d 50 f 6 COS(6:B) d3: = 8111(633) + C. If we substitute in = 6:1: then (1: = 6 and if we write this as du 2 6 do: then u du = cos(6w)6 do: = 6 cos(6a:) d3 and Part 2 of 3 f 6 cos(6:z:) dz = / cos(u) du: sin(u) + C so we have simplified the integral by making this u-substitution. Consider the related integral / cos(3m) dw. Making the substitution in = 32: now gives (hr = 3 tin: or do: = g (111.. Then f cos(3:c) do: = f % Sin(3x) syntax error. Check your variables - you might be using an incorrect one. du