simplify alpha test in Pyramid2

Sample/HardParticle/Pyramid2.cpp

@@ -45,12 +45,11 @@ std::string Pyramid2::validate() const
     requestGt0(errs, m_length, "length");
     requestGt0(errs, m_width, "width");
     requestGt0(errs, m_height, "height");
-    const double cot_alpha = Math::cot(m_alpha);
-    if (m_alpha <= 0 || !std::isfinite(cot_alpha) || cot_alpha < 0)
-        errs.push_back("pyramid angle alpha " + std::to_string(m_alpha) + " out of bounds");
+    requestIn(errs, m_alpha, "alpha", 0, M_PI_2);
     if (!errs.empty())
         return jointError(errs);
 
+    const double cot_alpha = Math::cot(m_alpha);
     double r = cot_alpha * 2 * m_height / m_length;
     double s = cot_alpha * 2 * m_height / m_width;
     if (r > 1)