#範例8-2：求矩陣的跡tracer
#跡tracer=對角線值相乘指令=np.trace(A)
import numpy as np
A = np.array([
    [-1,2,7,0],
    [3,5,-8,4],
    [1,2,7,-3],
    [4,-2,1,0]
    ])
print('A的跡tracer=',np.trace(A))