2022－2022英语周报七年级fjm答案

3.A【命题意图】本题考查二倍角公式、诱导公式、同角三角函数的基本关系,体现了逻辑推理、数学运算等核心素养多法解题·方法一由题意,知cosa≠0(若cos a=0, sin 2a-cos 2a-1=2sin acos a-2cos a=sin 2a+cos 2a+1 2sin acos a+2cos a0)sin 2a-cos 2a-1 2sin acos c-2cos ainl a+sin a+cos a tan a+1=2,tanα=3,sin a-cos a tan asin(5TT+a)cos a 1 1故选A.方法二由方法一知,cosα≠0,sin 2a +cos 2a+1sin 2a-cos 20-1sin a+cos a)+(cos a+sin a)( cos a-sin a)(cos a-sin a)"-(cos a+sin a)(cos a-sin a)(sin a+cos a)(2cos a)-(cos a-sin a)(2cos arsin (+ Cos (rsIn a- cos a7sin a=3cos a, tan o=3, sin(T+as a 1a tan a=3故选As名师评题本题是一道典型的给值求值题,解决问题的关键是将所给条件式进行化简并整理,对于条件式中分子、分母中的1,既可以与cos2a组合,利用升幂公式,同时将sin2a用二倍角公式展开,也可以将1与sin2a组合,奏成完全平方式,同时将cos2a化成co32a-sin3a,再利用因式分解来处理.对于三角恒等变换问题,要有强烈的目标意识,所给的目标式看起来比较复杂,用诱导公式即可化为单角,所以已知条件式中的二倍角化为单角也就顺其自然了

书面表达One possible version:NOTICEA sports meeting will be held in the playground of our school from next Thursday to FridayAs you know, the pressure of study is very heavy now, especially for those senior 3. So the purpose of the sports meeting is to letevery student get relaxed, as a result of which we students can live happily and heal thilyEveryone is welcome to take part in it. Those who perform excellently at the sports meeting will get prizes. But don' t take theresults so serously because taking part is more important than the result. Good luck to everyone!

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