(* Graded Homework Section 2.4: #6, 23, 48, p. 146 *)

#6

(* #6 *)
g[t_]:=4Sec[t]+Tan[t];
g'[t]

#23

(* #23 *)
f[x_]:=Cos[x]-Sin[x]
f'[x]
m=f'[Pi]
Simplify[m(x-Pi)+(-1)]
Plot[{f[x],m(x-Pi)+(-1)},{x,Pi/2,3Pi/2}]

#48

(* #48 *)
Limit[Sin[x-1]/(x^2+x-2),x->1]