Respuestas

2013-07-28T01:05:58+02:00
((cos)^(2))(B)=((1+cos(2B))/(2)) ,    ((cos)^(2))(B).((cos)^(2))(B)-((sin)^(2))(B)·((sin)^(2))(B)=((1+cos(2B))/(2))·((1+cos(2B))/(2))-((1-cos(2B))/(2))·((1-cos(2B))/(2))=((1+cos(2B))/(2))-((1-cos(2B))/(2))=((1+cos(2 B)-1+cos(2B))/(2))=((2cos(2B))/(2))=cos(2B).