標題:
唔識做功課56
發問:
solve the following equations for 0≤a<360. 1. cos a= - cos 45 2. tan a = - cos 17
最佳解答:
1. cos a = -cos45° cos a = -√2 / 2[Then, we know that a is in QII or QIII] a = 180° - 45° or a = 180° + 45° a = 135° or a = 225° 2. tan a = -cos17° tan a = -0.956304756[Then, we know that a is in QII or QV] [Use calculator to consider what value of b would give tan b = 0.956304756.] [It turns out that b = 43.72047703°.] Therefore, a = 180° - 43.72047703° or a = 360° - 43.72047703° a = 136.27952297° or a = 316.27952297° 2015-03-21 17:42:48 補充： In Q2, [Then, we know that a is in QII or QIV] 2015-03-22 23:17:01 補充： 為了令同學容易去明白和計算，使用以下的步驟： （１）先判斷是哪一個象限 (quadrant)：１，２，３，４ （２）不理正負，全部當正數計出角度（那麼這角度必定是小於 90°，稱為 a） （３）最後，根據（１）在以下四項中選適當的作答： a, 180° - a, 180° + a, 360° - a。 2015-03-22 23:18:26 補充： 例如：cos(x) = -0.6 （１）首先知道 x 是在 QII 或 QIII （２）然後想像 cos(a) = 0.6 得 a = 53.13° （３）答案是 x = 180° - 53.13° 或 x = 180° + 53.13° 2015-03-23 19:45:02 補充： 客氣啦~ 你咁勤力, 希望你可以考得好成績。
其他解答:
[Use calculator to consider what value of b would give tan b = 0.956304756.] [It turns out that b = 43.72047703°.]唔明点解要求出tan b,亦唔明白負0.9563...為何變成正0.9563...唔好意思呀,哩課有好多唔明白嘅地方,請知識長再指点一下！ 2015-03-23 18:44:22 補充： 其實miss冇教我當正數計出角度,所以我冇辦法計得到,我再將exercise重做咗一次,全對喇!所以...知識長好多謝你!
唔識做功課56
發問:
solve the following equations for 0≤a<360. 1. cos a= - cos 45 2. tan a = - cos 17
最佳解答:
1. cos a = -cos45° cos a = -√2 / 2[Then, we know that a is in QII or QIII] a = 180° - 45° or a = 180° + 45° a = 135° or a = 225° 2. tan a = -cos17° tan a = -0.956304756[Then, we know that a is in QII or QV] [Use calculator to consider what value of b would give tan b = 0.956304756.] [It turns out that b = 43.72047703°.] Therefore, a = 180° - 43.72047703° or a = 360° - 43.72047703° a = 136.27952297° or a = 316.27952297° 2015-03-21 17:42:48 補充： In Q2, [Then, we know that a is in QII or QIV] 2015-03-22 23:17:01 補充： 為了令同學容易去明白和計算，使用以下的步驟： （１）先判斷是哪一個象限 (quadrant)：１，２，３，４ （２）不理正負，全部當正數計出角度（那麼這角度必定是小於 90°，稱為 a） （３）最後，根據（１）在以下四項中選適當的作答： a, 180° - a, 180° + a, 360° - a。 2015-03-22 23:18:26 補充： 例如：cos(x) = -0.6 （１）首先知道 x 是在 QII 或 QIII （２）然後想像 cos(a) = 0.6 得 a = 53.13° （３）答案是 x = 180° - 53.13° 或 x = 180° + 53.13° 2015-03-23 19:45:02 補充： 客氣啦~ 你咁勤力, 希望你可以考得好成績。
其他解答:
[Use calculator to consider what value of b would give tan b = 0.956304756.] [It turns out that b = 43.72047703°.]唔明点解要求出tan b,亦唔明白負0.9563...為何變成正0.9563...唔好意思呀,哩課有好多唔明白嘅地方,請知識長再指点一下！ 2015-03-23 18:44:22 補充： 其實miss冇教我當正數計出角度,所以我冇辦法計得到,我再將exercise重做咗一次,全對喇!所以...知識長好多謝你!
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