You are making really strange errors . . .
Product Rule . . .
Chain Rule . . .
Calculate y' for:
1. y= x sinh(x^2)
I got to: y'= cosh x^2(2x) ....
2. y= ln(cosh 3x)
I got to: y= 1/cosh 3x (cosh 3x)
= sinh 3/cosh 3x...
I don't think these calculations are correct. Please help me. Thanks.