He is going to join a soccer fan club next month.改为同义句

He will join a soccer fan club next month.
be going to与will两者都可表示将要发生的事、将要去做某事,但它们有如下几点区别：
1.be going to 表示近期、眼下就要发生的事情,will 表示的将来时间则较远一些,如：
He is going to write a letter tonight.He will write a book one day.
2.be going to 表示根据主观判断将来肯定发生的事情,will表示客观上将来势必发生的事情.
He is seriously ill.He is going to die.He will be twenty years old.
3.be going to含有“计划,准备”的意思,而will则没有这个意思,如：She is going to lend us her book.He will be here in half an hour.
4.在有条件从句的主句中,一般不用 be going to,而多用will,如：If any beasts come at you,I'll stay with you and help you will和be going to的选用原则 1.关于“打算”
原先作好的打算用“be going to”.
“Kate is in hospital.” “Yes,I know.I am going to see her this afternoon.” “凯特在住院.”“是的,我知道.我下午要去看她.” 说话时即时的打算用“will”.
“Kate is in hospital.” “Oh,really,I didn’t know.I will go and see her at once.” “凯特在住院.”“哦,是吗?我都不知道呢.我得马上去看她.”
2.关于“预料”
在有迹象表明的情况下的预料用“be going to” Look at the clouds.It’s going to rain.你看天上的云.快下雨了.My God!We are going to crash.天哪!我们快撞车了.
在没有迹象表明的情况下进行的猜测用“will,be going to”皆可.I think the weather will be nice.I think the weather is going to be nice.我想天会晴朗.
Do you think the car will start?Do you think the car is going to start?你想车能发动起来吗?
当动词表示内心活动时,表示猜测的句子必须用“will” I think she will like the cake I made for her.我想她会喜欢我为她做的蛋糕.
"be going to"中的be是助动词,它有am,is,are三种形式,没有什么实际意义；to是动词不定式的标志词,标志词后动词用原形.它们三个总是形影不离,在句中共同表达"计划、打算、准备去做……"的意思.如：
I am going to sell this old car,and buy a new one.我打算卖掉这辆旧车,然后买辆新车."be going to"必须与表示将来的时间信息词如this afternoon,tomorrow,the day
after tomorrow以及next系列时间短语等连用.它可表示：1.事先经过考虑、安排近期要做的事情.如：
They are going to the park this weekend.他们打算这周末去公园.2.根据目前某种迹象判断某事非常有可能发生.如：
What bad weather!It is going to snow tomorrow.多糟的天气!看来明天要下雪.另外
1."be going to"的肯定式是"主语 + be going to + do(动词原形) + ...".上面的例句中就有肯定句,再仔细看看吧!
2."be going to"的否定式是在助动词be后加not,即：主语 + be + not + going to + do +...如：
Peter is not going to make a model ship.彼得不打算做一个轮船模型.3."be going to"的疑问式是把助动词be移到句首,即：Be+主语+going to do+...这和be作联系动词时的用法相似.如：
Are you going to mend his chair soon?Yes,I am./ No,I'm not.你打算马上给他修椅子吗?是的,马上修./不,没这个想法.