高一数学,急,,,,
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(1)3根号15sinx+3根号5cosx =6根号5((根号3)/2sinx+1/2cosx) =6根号5(cos10°sinx+sin30°cosx) =(6根号5)sin(x+30°) (2)3/2cosx-根号3/2sinx 原式=√3(√3/2cosx-1/2sinx) =√3(sinπ/3cosx-cosπ/3sinx) =√3sin(π/3-x) (3)根号3sinx/2+cosx/2 =2(根号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° =根号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)特别简单,套正弦余弦公式就Ok了,注意符号(9)(tan5π/4+tan5π/12)/(1-tan5π/12) 根据tan的和角公式: tan(x+y)=(tanx+tany)/(1-tanxtany) 再根据诱导公式:tan 5π/4 = tan(π+π/4) =tan π/4 所以 (tan 5π/4 + tan 5π/12)/(1-tan 5π/12) (诱导公式,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 =-根号3 综上,原式= -根号3. (10)(sin(x+p)-2sinxcosp)/2sinxsinp+cos(x+p) =(cosxsinp-sinxcosp)/(sinxsinp+cosxcosp) =sin(p-x)/cos(p-x) =tan(p-x)
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