Ângulo entre reta e plano, e ângulo entre planos

Synopsis: In this class we define the notions of angle between line and plane and angle between planes. To exemplify, we compute the angle between a side face and the base of a quadrangular pyramid whose edges are all congruent.
Source: Portal of Mathematics.
URL: http://matematica.obmep.org.br/index.php/modulo/ver?modulo=27&tipo=1#