设△ABC,AB=5,AC=7,斜边BC.BC^2=AB^2+AC^2 => BC^2=25+49=74 =>BC=√74=8.6023252ABBCcos∠ABC=AB^2+BC^2-AC^2 =>∠ABC=arccos5/8.602325=542ACBCcos∠ACB=AC^2+BC^2-AB^2 =>∠ACB=arccos7/8.602325=36一个直角三角形,给两条直角边2.5和7,如何求出其余两角角度及斜边的长 这个也帮忙算一下