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  • 137頁13題答案

    137頁13題答案
    數(shù)學(xué)人氣:311 ℃時間:2020-06-14 10:35:12
    優(yōu)質(zhì)解答
    是不是這個

    (1)3根號15sinx+3根號5cosx
    =6根號5((根號3)/2sinx+1/2cosx)
    =6根號5(cos10°sinx+sin30°cosx)
    =(6根號5)sin(x+30°)
    (2)3/2cosx-根號3/2sinx
    原式=√3(√3/2cosx-1/2sinx)
    =√3(sinπ/3cosx-cosπ/3sinx)
    =√3sin(π/3-x)
    (3)根號3sinx/2+cosx/2
    =2(根號3/2sinx/2+1/2cosx/2)
    =2(cos30°sinx/2+sin30°cosx/2)
    =2sin(x/2+30°)
    (4)√2/4sin(π/4-x)+√6/4cos(π/4-x)
    =√2/2(1/2*sin(π/4-x)+√3/2cos(π/4-x))
    =√2/2(cosπ/3*sin(π/4-x)+sinπ/3*cos(π/4-x))
    =√2/2sin(π/4-x+π/3)
    =√2/2sin(7π/12-x)
    (5)sin347°cos148°+sin77°cos58°
    =sin(360°-13°)cos(180°-32°)+cos13°sin32°
    =sin13°cos32°+cos13°sin32°
    =sin(13+32)°
    =sin45°
    =根號2/2
    (6)sin164°sin224°+sin254°sin314°
    =sin16°(-sin44°)+(-sin74°)(-sin46°)
    =sin74°sin46°-sin16°sin44°
    =sin74°cos44°-cos74°sin44°
    =sin(74°-44°)
    =sin30
    =1/2
    (7)(8)特別簡單,套正弦余弦公式就Ok了,注意符號
    (9)(tan5π/4+tan5π/12)/(1-tan5π/12)
    根據(jù)tan的和角公式:
    tan(x+y)=(tanx+tany)/(1-tanxtany)
    再根據(jù)誘導(dǎo)公式:tan 5π/4 = tan(π+π/4) =tan π/4
    所以
    (tan 5π/4 + tan 5π/12)/(1-tan 5π/12) (誘導(dǎo)公式,并利用tan π/4=1)
    =(tan π/4 + tan 5π/12)/(1-tan π/4*tan 5π/12) (由tan的和角公式)
    =tan(π/4 + 5π/12)
    =tan 2π/3
    =-根號3
    綜上,原式= -根號3.
    (10)(sin(x+p)-2sinxcosp)/2sinxsinp+cos(x+p)
    =(cosxsinp-sinxcosp)/(sinxsinp+cosxcosp)
    =sin(p-x)/cos(p-x)
    =tan(p-x)沒題目啊,你把題目發(fā)上來,我?guī)湍阕觥?、原式=sin[(α+β)-(β-γ)]=sin(α+γ) 8、原式=-cos[(α-β)+(β-γ)]=-cos(α-γ)
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