| 結果3pi |
| 送交者: zhf 2020月01月18日10:12:20 於 [靈機一動] 發送悄悄話 |
| 回 答: 趣味的數學-226 由 gugeren 於 2020-01-16 19:06:39 |
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tan x = (9+sqrt(77))/2, (9-sqrt(77))/2 根的和= arctan[(9+sqrt(77))/2]+arctan[(9-sqrt(77))/2]+ arctan[(9+sqrt(77))/2]+π+arctan[(9-sqrt(77))/2]+π= 2(arctan[(9+sqrt(77))/2]+arctan[(9-sqrt(77))/2])+2π 因[(9+sqrt(77))/2][(9-sqrt(77))/2]=1 arctan[(9+sqrt(77))/2]+arctan[(9-sqrt(77))/2]=π/2 根的和=3π |
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