diff --git a/luku21.tex b/luku21.tex
index 68aaee3..dd12ddc 100644
--- a/luku21.tex
+++ b/luku21.tex
@@ -697,8 +697,8 @@ For example, the number 11 is prime, because
 and the number 12 is not prime, because
 \[11! \bmod 12 = 0 \neq 11.\]
 
-Hence, Wilson's theorem tells us whether a number
-is prime. However, in practice, the theorem cannot be
+Hence, Wilson's theorem can be used to find out
+whether a number is prime. However, in practice, the theorem cannot be
 applied to large values of $n$, because it is difficult
 to calculate the value of $(n-1)!$ when $n$ is large.