be in good 在...表现良好,在...有效果 但be good in 极少作文固定短语
It has been proved to be good in practice result.实践效果良好.
To have fine political and professional quality and to be good in conduct.
有良好的政治、业务素质和良好的品行;
be good at 擅长于 ...at后面跟名词或动名词（即动词+ing）
Alex is very good at languages.擅长语言
She's good at making things.