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tAn20°+4sin20°

直接用数字表示角度了,即20表示20度。 tan20+4sin20 =sin20/cos20+4sin20 (通分) =(sin20+4sin20cos20)/cos20 (由倍角公式:2sin20cos20=sin40) =(sin20+2sin40)/cos20 =[(sin20+sin40)+sin40]/cos20 (对sin20+sin40用和差化积公式) =(2sin30co...

tan20°+4sin20°= sin20°+4sin20°cos20° cos20° = sin20°+2sin40° cos20° = (sin20°+sin40°)+sin40° cos20° = 2sin30°cos10°+sin40° cos20° = cos10°+sin40° cos20° = sin80°+sin40° cos20° = 2sin60°cos20° cos20° =2sin60°= 3 .故答案为: 3 .

tan20°+4sin20°=sin20°+4sin20°cos20°cos20°=sin20°+2sin40°cos20°=(sin20°+sin40°)+sin40°cos20°=2sin30°cos10°+sin40°cos20°=sin80°+sin40°cos20°=2sin60°cos20°cos20°=2sin60°=3.

tan20'+4sin20' =(sin20+2sin40)/cos20 =(sin20+sin40+sin40)/cos20 =(2sin30cos10+sin40)/cos20 =(cos10+sin40)/cos20 =(sin80+sin40)/cos20 =2sin60cos20/cos20=2sin60 =根号3

tan20°+4sin20° =(sin20°+2sin40°)/cos20° =(sin20°+sin40°+sin40°)/cos20° =(2sin30°cos10°+sin40°)/cos20° =(cos10°+sin40°)/cos20° =(sin80°+sin40°)/cos20° =2sin60°cos20°/cos20°=2sin60° =根号3

sin20°=0.3420 cos20°=0.9397 tan20°=0.3640

解: (4sin20º-3tan10º)cos10º =4sin20ºcos10º-3sin10º =2(sin30º+sin10º)-3sin10º =1-sin10º 原式=√3tan10ºcos10º/(4sin20º-3tan10º) cos10º =√3sin10º/...

tan20+4sin20 =sin20/cos20+4sin20 =(sin20+4sin20cos20)/cos20 =(sin20+2sin40)/cos20 =(sin20+sin40+sin40)/cos20 =(2sin30cos10+sin40)/cos20 =(cos10+sin40)/cos20 =(sin80+sin40)/cos20 =2sin60cos20/cos20 =2sin60 =根号3

(1+cos20°)/2sin20°]-sin10°(1/tan5°-tan5°) =[(1+cos20°)/2sin20°]-sin10°(cot5°-tan5°) =[(1+cos20°)/4sin10°cos10°]-sin10°(cot5°-tan5°) =(2cos10°/4sin10°)-2sin5°cos5°(cot5°-tan5°) =(cos10°/2sin10°)-2((cos5°)^2-(sin5°)^2) =(cos10...

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