2016年高三第一轮复习 金版教程选3-4-1-2
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题组一 双基练1. [2021·福州高三期末]如图所示,一束光线从折射率为1.5的玻璃内射向空气,在界面上的入射角为45°,下面四个光路图中,正确的是 ( )解析:本题考查全反射条件.光从玻璃射向空气,是从光密介质射向光疏介质,由于玻璃的折射率n =1.5,因此发生全反射的临界角sin C =1n =23<22,所以C <45°,因此图中的光会发生全反射,A 项正确.答案:A2. [2022·福建高三仿真模拟]如图所示,有一束光投射到放在空气中的平行玻璃砖的表面Ⅰ上,下列说法中正确的是 ( )A. 假如在界面Ⅰ上入射角大于临界角,光将不会进入玻璃砖B. 光从界面Ⅱ射出时出射光线可能与最初的入射光线不平行C. 光进入界面Ⅰ后可能不从界面Ⅱ射出D. 不论光从什么角度入射,都能从界面Ⅱ射出解析:发生全反射的必要条件有两个,即光从光密介质射入光疏介质和入射角不小于临界角,本题中光从空气射入界面Ⅰ上时,光是从光疏介质射入光密介质,所以即使入射角大于临界角,光也不会发生全反射现象,光会进入玻璃砖,选项A 错误;由于光的上、下两个界面平行,光从界面Ⅱ射出时出射光线确定会与最初的入射光线平行,选项B 错误;光进入界面Ⅰ后,从玻璃射向界面Ⅱ时的入射角确定小于临界角,光确定会从界面Ⅱ射出,选项C 错误;不论光从什么角度入射,都能从界面Ⅱ射出,选项D 正确.答案:D3. 夜间行车光照在警示标志上后反射回来特殊醒目,主要是由于警示标志是由球形的反射物制成,如图,假设反射物为分布均匀的球形,其折射率为 3.某次灯光照射在该标志上后,经球形物一系列的折射和反射后,出射光线恰与入射光线平行,则第一次的入射角( )A. 30°B. 45°C. 60°D. 15°解析:设入射角为i ,折射角为θ,作出光路图,由于出射光线恰好和入射光线平行,所以i =2θ,依据折射定律sin i sin θ=sin2θsin θ=3,所以θ=30°,i =2θ=60°.答案:C4. [2022·江苏南京]如图甲所示,在安静的湖面下有一个点光源S ,它发出的是两种不同颜色的a 光和b光,在水面上形成了一个被照亮的圆形区域,该区域的中间为由ab 两种单色光构成的复色光的圆形区域,周边为环状区域,且为a 光的颜色(图乙为俯视图).则以下说法中正确的是 ( )A. 水对a 光的折射率比b 光的大B. a 光在水中的传播速度比b 光的大C. a 光的频率比b 光的大D. 在同一装置的杨氏双缝干涉试验中,a 光的干涉条纹比b 光窄解析:依据“周边为环状区域,且为a 光的颜色”知,点光源射向水面的单色光b 在环形区域内边界处发生全反射,而单色光a 在外边界处发生全反射,即水对单色光b 的临界角C 较小,由sin C =1n 可确定水对单色光a 的折射率比b 光的小,A 项错误;由折射率公式n =cv 知,a 光在水中的传播速度比b 光的大,B 项正确;a 光的频率比b 光的小,C 项错误;a 光的波长比b 光的大,干涉条纹间距与波长成正比,所以在同一装置的杨氏双缝干涉试验中,a 光的干涉条纹比b 光的宽,D 项错误.答案:B5. 如图所示的长直光纤,柱芯为玻璃,外层以折射率较玻璃低的介质包覆.若光线自光纤左端进入,与中心轴的夹角为θ,则下列有关此光线传播方式的叙述正确的是( )A. 不论θ为何值,光线都不会发生全反射B. 不论θ为何值,光线都会发生全反射C. θ够小时,光线才会发生全反射D. θ够大时,光线才会发生全反射解析:发生全反射的条件之一是入射角i 要大于等于临界角C ,即光线传播到光纤侧面时的入射角i 应满。
Ⅰ.阅读理解(建议用时16′)A[2016·山东诊断]A rare butterfly has been discovered in Britain for the first time in 60 years, having moved from Eastern Europe. The only previous record of a wild yellow-legged Tortoiseshell in Britain was in 1953, when it was seen just once in Sevenoaks, Kent. Several weeks ago, there were already four confirmed sightings, along the East coast in Norfolk, Suffolk and Kent, and six further reports of the butterfly in coastal areas. Conser v ationists are v ery excited about the sightings, w hich are rare in the butterfly w orld.SThe butterflies are thought to have flown on easterly winds across Europe in the last few weeks. The large and colourful insect mainly lives in Eastern Europe. In recent years, it has spread W1into Scandinavia and its number increases rapidly during warm weather. Also known as the Scarce Tortoiseshell, it has an orange and blue colour and is about one third bigger than our own Small Tortoiseshell.Butterfly Conservation was starting its annual W2Big Butterfly Count, a yearly survey of the butterflies across the nation. Sir David Attenborough, President of the charity, said, “The UK is a nation of amateur naturalists and we have a proud tradition of celebrating and studying our wildlife. By taking part in P1the Big Butterfly Count this summer, you can contribute to discovering the fantastic W3butterflies and other wildlife that share your garden, parks and countryside.”He added, “Butterflies_fought_back last year after a terrible 2012 but despite this, butterfly numbers were still below a v erage W4. Three quarters of the UK's butterflies are in decline W5and one third are in danger of dying out P2. This is bad news for the UK's birds, bees, bats and other wildlife.本文讲述的是一种稀有蝴蝶最近在美国被发现,并讲述了与保护蝴蝶有关的一些情况。
第三节 两角和与差及二倍角三角函数公式 题号1 2 3 4 5 6 答案1.计算1-2sin 222.5°的结果等于( )A.12B.22C.33D.32解析:原式=cos 45°=22.故选B. 答案:B2.设tan(α+β)=25,tan ⎝ ⎛⎭⎪⎫β-π4=14,则tan ⎝⎛⎭⎪⎫α+π4的值是( ) A.318 B.322 C.1318 D .-1322解析:tan ⎝ ⎛⎭⎪⎫α+π4=tan ⎣⎢⎡⎦⎥⎤(α+β)-⎝⎛⎭⎪⎫β-π4=322. 答案:B3.求值:⎝ ⎛⎭⎪⎫cos π12-sin π12⎝ ⎛⎭⎪⎫cos π12+sin π12=( ) A .-32 B .-12C.12D.32答案:D4.若tan θ+1tan θ=4,则sin 2θ=( ) A.15 B.14C.13D.12解析:由tan θ+1tan θ=4得,sin θcos θ+cos θsin θ=sin 2θ+cos 2θsin θcos θ=4,即112sin 2θ=4,∴si n 2θ=12.故选D.答案:D5.sin 47°-sin 17°cos 30°cos 17°=( ) A .-32 B .-12 C.12 D.32解析:sin 47°-sin 17°cos 30°cos 17°=sin (17°+30°)-sin 17°cos 30°cos 17° =sin 17°cos 30°+cos 17°sin 30°-sin 17°cos 30°cos 17°=sin 30°=12.故选C. 答案:C6.已知α,β都是锐角,cos 2α=-725,cos(α+β)=513,则sin β=( ) A.1665 B.1365 C.5665 D.3365解析:∵cos 2α=2cos 2α-1,cos 2α=-725,又α为锐角, ∴cos α=35, sin α=45. ∵cos(α+β)=513,∴(α+β)为锐角,sin(α+β)=1213. ∴sin β=sin [](α+β)-α=sin(α+β)cos α-cos(α+β)sin α=1213×35-513×45=1665.故选A. 答案:A7.(2013·上海卷)若cos xcos y +sin xsin y =13,则cos(2x -2y)=________. 解析:cos x cos y +sin x sin y =cos(x -y )=13, 所以cos 2(x -y )=2cos 2(x -y )-1=-79. 答案:-798.sin α=35,cos β=35,其中α,β∈⎝ ⎛⎭⎪⎫0,π2,则α+β=______.解析:∵α,β∈⎝⎛⎭⎪⎫0,π2,sin α=35,cos β=35, ∴cos α=45,sin β=45. ∴cos(α+β)=cos αcos β-sin αsin β=0.∵α,β∈⎝⎛⎭⎪⎫0,π2,∴0<α+β<π,故α+β=π2. 答案:π29.已知tan α=2,则2sin 2α+1sin 2α=________. 解析:2sin 2α+1sin 2α=3sin 2α+cos 2α2sin αcos α=3tan 2α+12tan α=3×22+12×2=134. 答案:13410.已知α为锐角,且cos ⎝⎛⎭⎪⎫α+π4=35,则sin α=__________. 解析:因为α为锐角,所以α+π4∈⎝ ⎛⎭⎪⎫π4,3π4, 因为cos ⎝⎛⎭⎪⎫α+π4=35, 所以sin ⎝ ⎛⎭⎪⎫α+π4= 1-cos 2⎝ ⎛⎭⎪⎫α+π4=45, 则sin α=sin ⎣⎢⎡⎦⎥⎤⎝⎛⎭⎪⎫α+π4-π4=sin ⎝ ⎛⎭⎪⎫α+π4cos π4-cos ⎝ ⎛⎭⎪⎫α+π4sin π4=45×22-35×22=210. 答案:21011.已知函数f(x)=cos 2x +sin xcos x ,x ∈R.(1)求f ⎝ ⎛⎭⎪⎫π6的值; (2)若sin α=35,且α∈⎝ ⎛⎭⎪⎫π2,π,求f ⎝ ⎛⎭⎪⎫α2+π24. 解析:(1)f ⎝ ⎛⎭⎪⎫π6=cos 2π6+sin π6cos π6=⎝ ⎛⎭⎪⎫322+12×32=3+34. (2)f (x )=cos 2x +sin x cos x=1+cos 2x 2+12sin 2x =12+12(sin 2x +cos 2x ) =12+22sin ⎝⎛⎭⎪⎫2x +π4,f ⎝ ⎛⎭⎪⎫α2+π24=12+22sin ⎝ ⎛⎭⎪⎫α+π12+π4 =12+22sin ⎝⎛⎭⎪⎫α+π3 =12+22⎝ ⎛⎭⎪⎫sin α·12+cos α·32. 因为sin α=35,且α∈⎝ ⎛⎭⎪⎫π2,π,所以cos α=-45, 所以f ⎝ ⎛⎭⎪⎫α2+π24=12+22⎝ ⎛⎭⎪⎫35×12-45×32=10+32-4620. 12.已知函数f(x)=sin ⎝⎛⎭⎪⎫ωx +π6(ω>0)的最小正周期为π. (1)求ω的值;(2)设α∈⎝ ⎛⎭⎪⎫0,π2,β∈⎝ ⎛⎭⎪⎫π2,π,f ⎝ ⎛⎭⎪⎫-12α+π6=35,f ⎝ ⎛⎭⎪⎫12β+5π12=-1213,求sin(α+β)的值. 解析:(1)∵函数f (x )=sin ⎝⎛⎭⎪⎫ωx +π6的最小正周期为π,且ω>0,∴2πω=π, ∴ω=2.(2)由(1)得f (x )=sin ⎝⎛⎭⎪⎫2x +π6, ∴f ⎝ ⎛⎭⎪⎫-12α+π6=sin ⎣⎢⎡⎦⎥⎤2⎝ ⎛⎭⎪⎫-12α+π6+π6 =sin ⎝ ⎛⎭⎪⎫π2-α=cos α=35. ∵α∈⎝⎛⎭⎪⎫0,π2, ∴sin α=1-cos 2α=45. 又f ⎝ ⎛⎭⎪⎫12β+5π12=sin ⎣⎢⎡⎦⎥⎤2⎝ ⎛⎭⎪⎫12β+5π12+π6=sin(π+β)=-sin β=-1213, ∴sin β=1213. ∵β∈⎝ ⎛⎭⎪⎫π2,π, ∴cos β=-1-sin 2β=-513, ∴sin(α+β)=sin αcos β+cos αsin β=45×⎝ ⎛⎭⎪⎫-513+35×1213=1665.。