Pro tip: Install python and do your calculations on the command line.
from numpy import *
from numpy import array as c
from math import *
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
The Windows 7 calculator is a solid basic calculator, but I think most power users in that time used third-party options or something like a spreadsheet. Microsoft clearly thinks of the calculator as a demo application for UWP and XAML, as evidenced by them open-sourcing it, sort of like how Apple treats TextEdit like a Cocoa text rendering demo. If you want a serious calculator or a serious text editor, you're better off looking outside these bundled tools.
Can't live without that one in $PATH.