Fix typo in Misra1c NIST problem.

The exponent is -0.5, not 0.5.

Change-Id: I77c7bd2ed2b9b20e83d830f74c73088c1b3b3435

examples/nist.cc

diff --git a/examples/nist.cc b/examples/nist.cc
index f78d8eb..fb85beb 100644
--- a/examples/nist.cc
+++ b/examples/nist.cc
@@ -242,7 +242,7 @@
 
 // y = b1 * (1-(1+2*b2*x)**(-.5))  +  e
 NIST_BEGIN(Misra1c)
-  b[0] * (T(1.0) - pow(T(1.0) + T(2.0) * b[1] * x, 0.5))
+  b[0] * (T(1.0) - pow(T(1.0) + T(2.0) * b[1] * x, -0.5))
 NIST_END
 
 // y = b1*b2*x*((1+b2*x)**(-1))  +  e