Adjust expected precision.

Author: jzmaddock

test/test_autodiff_5.cpp

@@ -59,10 +59,10 @@ BOOST_AUTO_TEST_CASE_TEMPLATE(chebyshev_hpp, T, all_float_types) {
       BOOST_CHECK_CLOSE(
           boost::math::chebyshev_t(n, make_fvar<T, m>(x)).derivative(0u),
           boost::math::chebyshev_t(n, x), 40 * test_constants::pct_epsilon());
-
+      // Lower accuracy with clang/apple:
       BOOST_CHECK_CLOSE(
           boost::math::chebyshev_u(n, make_fvar<T, m>(x)).derivative(0u),
-          boost::math::chebyshev_u(n, x), 40 * test_constants::pct_epsilon());
+          boost::math::chebyshev_u(n, x), 80 * test_constants::pct_epsilon());
 
       BOOST_CHECK_CLOSE(
           boost::math::chebyshev_t_prime(n, make_fvar<T, m>(x)).derivative(0u),