calbin needs a grapher (but java sucks and is so hard) so here is a python one that is simple

calbin.py

import matplotlib.pyplot as plt
import numpy as np

# 100 linearly spaced numbers
x = np.linspace(-5,5,100)

# the users input


## REFORMATTING
def reformat(string):
    string = string.replace("sin","np.sin")
    string = string.replace("cos","np.cos")
    string = string.replace("tan","np.tan")
    string = string.replace("^","**")
    return string


def graph(equation):
    y = eval(reformat(equation))


        # setting the axes at the centre
    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1)
    ax.spines['left'].set_position('center')
    ax.spines['bottom'].set_position('zero')
    ax.spines['right'].set_color('none')
    ax.spines['top'].set_color('none')
    ax.xaxis.set_ticks_position('bottom')
    ax.yaxis.set_ticks_position('left')

    # plot the function
    plt.plot(x,y, 'r')

    # show the plot
    plt.savefig("graph.png")
    plt.show()
    

    return plt

graph("sin(x)")