Just need help with #3 and #4. Thank you

Establish the following identities: 1. sinh(x + y) = sinh(x) cosh(y) + sinh(y) cosh(x) 2. cosh(x + y) = cosh(x) cosh(y) + sinh(x) sinh(y) 3. tanh(x + y) = tanh(x) + tanh(y) 1 + tanh(x) tanh(y) 4. sinh(2x) = 2 sinh(x) cosh(x) Hint: To do these, really just use the definition of cosh() _ e te and sinh(x) = 2 er - e-x , tanh(x) _ sinh(x) 2 cosh (a) ed _ p-x , and properties of the natural exponential function ex