if this is in cosine originally how can i get it to represent sinisoidal

this is my code

iSol - 2*exp(-40*t) + 80*t*exp(-40*t) clc; clear; close all; % symbolic definitions: syms t i(t) diodt % variable: R1=3; R2=2; R3=5; L=62.5e-3; C=0.01; Vs=20; %Analysis for t: kvl_to=10*R3+L* diodt-Vo==0; diodt=solve(kvl_to, diodt) iC=-i; %#ok % passive sign convention didt=diff(i,t); VR=i*R3; VL=L*didt; v=1/c*int(ic); diffEqn=VR+VL-v==0; diffEqn=diff(diffEqn,t); % take d/dt both sides iSol=dsolve (diffEqn, [i(0)==10, didt(0)==diOdt]) iSol - 2*exp(-40*t) + 80*t*exp(-40*t) clc; clear; close all; % symbolic definitions: syms t i(t) diodt % variable: R1=3; R2=2; R3=5; L=62.5e-3; C=0.01; Vs=20; %Analysis for t: kvl_to=10*R3+L* diodt-Vo==0; diodt=solve(kvl_to, diodt) iC=-i; %#ok % passive sign convention didt=diff(i,t); VR=i*R3; VL=L*didt; v=1/c*int(ic); diffEqn=VR+VL-v==0; diffEqn=diff(diffEqn,t); % take d/dt both sides iSol=dsolve (diffEqn, [i(0)==10, didt(0)==diOdt])