GH-102341: Improve the test function for pow (#102342)

Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu>

Lib/test/test_pow.py

@@ -19,12 +19,11 @@ def powtest(self, type):
  self.assertEqual(pow(2, i), pow2)
  if i != 30 : pow2 = pow2*2
 
- for othertype in (int,):
- for i in list(range(-10, 0)) + list(range(1, 10)):
- ii = type(i)
- for j in range(1, 11):
- jj = -othertype(j)
- pow(ii, jj)
+ for i in list(range(-10, 0)) + list(range(1, 10)):
+ ii = type(i)
+ inv = pow(ii, -1) # inverse of ii
+ for jj in range(-10, 0):
+ self.assertAlmostEqual(pow(ii, jj), pow(inv, -jj))
 
  for othertype in int, float:
  for i in range(1, 100):