,解直角三角形的應(yīng)用,坡度、坡角和方位角,超市里有兩個(gè)自動(dòng)扶梯,你認(rèn)為哪一個(gè)比較陡?,如何用數(shù)學(xué)方法描述一個(gè)坡度呢？請(qǐng)你自學(xué)書(shū)上127頁(yè)，標(biāo)記出“坡腳”、“坡度”的意義。,公式： 坡度= ,坡面的鉛垂高度（h）和水平寬度（l）的比叫做坡面的坡度（或坡比）。,坡面與水平面所夾的銳角叫做坡角。,坡比越大，山坡越陡,用數(shù)學(xué)去解釋生活,如圖,正切也經(jīng)常用來(lái)描述山坡的坡度.例如，有一山坡在水平方向上每前進(jìn)100m就升高60m,那么山坡的坡度i(即tan)就是:,你會(huì)算嗎？,1、坡角=45°坡比i=,11,30°,現(xiàn)在，你會(huì)通過(guò)計(jì)算坡度來(lái)解釋哪個(gè)扶梯更陡嗎？,解:甲梯中,乙梯中,tantan,乙梯更陡.,在生活中,常用一個(gè)銳角的正切表示梯子的傾斜程度.,小試牛刀,我軍某部在一次野外訓(xùn)練中，有一輛坦克準(zhǔn)備通過(guò)一座小山，已知山腳和山頂?shù)乃骄嚯x為1000米，山高為565米，如果這輛坦克能夠爬300 的斜坡，試問(wèn)：它能不能通過(guò)這座小山？,如圖，攔水壩的橫斷面為梯形ABCD（圖中i=1:3是指坡面的鉛直高度DE與水平寬度CE的比），根據(jù)圖中數(shù)據(jù)求： （1）坡角a和; （2）壩頂寬AD和斜坡AB的長(zhǎng)（精確到0.1m）,解：（1）在RtAFB中，AFB=90°,在RtCDE中，CED=90°,方位角,第二部分,如圖：點(diǎn)A在O的北偏東30° 點(diǎn)B在點(diǎn)O的南偏西45°（西南方向）,方位角,指南或指北的方向線與目標(biāo)方向線構(gòu)成小于900的角,叫做方位角.,口訣“上北下南左西右東”,你知道怎么描述圖中的方位嗎？,如圖，一艘輪船位于燈塔P的北偏東60°方向，距離燈塔80海里的A處，它沿正南方向航行一段時(shí)間后，到達(dá)位于燈塔P的南偏東30°方向上的B處，這時(shí)，海輪所在的B處距離燈塔P有多遠(yuǎn)？ （精確到0.01海里）,P,B,C,A,M,N,80,海中有一個(gè)小島A，它的周?chē)?海里范圍內(nèi)有暗礁，漁船跟蹤魚(yú)群由西向東航行，在B點(diǎn)測(cè)得小島A在北偏東60°方向上，航行12海里到達(dá)C點(diǎn)，這時(shí)測(cè)得小島A在北偏東30°方向上，如果漁船不改變航線繼續(xù)向東航行，有沒(méi)有觸礁的危險(xiǎn)？,B,A,C,D,12,M,分析：繼續(xù)航行是否安全，取決于小島A到BC航線的距離是否大于8海里。,CONTENTS,單擊此處添加標(biāo)題,Click here to add words,01,單擊此處添加標(biāo)題,Click here to add words,02,單擊此處添加標(biāo)題,Click here to add words,03,單擊此處添加標(biāo)題,Click here to add words,04,單擊此處添加標(biāo)題,Click here to add words,添加標(biāo)題,Click here to add words,Click here to add words,添加標(biāo)題,Click here to add words,Click here to add words,添加標(biāo)題,Click here to add words,Click here to add words,單擊此處添加標(biāo)題,Click here to add words,添加標(biāo)題,Click here to add words,Click here to add words,添加標(biāo)題,Click here to add words,Click here to add words,添加標(biāo)題,Click here to add words,Click here to add words,添加標(biāo)題,Click here to add words,Click here to add words,單擊此處添加標(biāo)題,Click here to add words,添加標(biāo)題,Click here to add words,Click 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