Understanding Matplotlib Legend Display

In order to display multiple line graphs on a single graph in matplotlib's pyplot, I would like you to teach me how to attach legends.

Now, multiple lines are stored in one variable and can be drawn in a single pyplot.At that time, I don't know how to add a legend.

The following example shows the sine and cosine functions of a trigonometric function at once, but how should I add a legend?(I didn't know what to do with the label argument)

import numpy as np
from matplotlib import pyplot as plt

x = np.linspace (1,10,100)

y1 = np.sin(x).reshape(-1,1)
y2 = np.cos(x).reshape(-1,1)
y=np.concatenate([y1,y2],axis=1)

plt.plot(x,y,label=)
plt.legend()

When I looked up the net, there was an example of drawing pyplots separately and specifying label as an argument each time, but I couldn't find an example of how to display the legend at once.