有條數學唔識計…有無人識計呀---教下我－wszspj2的部落格

標題:

有條數學唔識計…有無人識計呀???教下我

發問:

1. In the figure, the perimeter of △ABC is 21cm.(a)Find BC(b)Find ∠BAC(c)Find the ares of △ABC2. In △ABC, BC = 10cm, ∠ABC =35°and ∠BAC =80° (a) Find AC.3. For the arithmetic series 7+15+.....+159, find (a) the number of terms n (b) the 5th term T(5) (c) the sum of the series S(n)4. (a) Solve... 顯示更多 1. In the figure, the perimeter of △ABC is 21cm. (a)Find BC (b)Find ∠BAC (c)Find the ares of △ABC 2. In △ABC, BC = 10cm, ∠ABC =35°and ∠BAC =80° (a) Find AC. 3. For the arithmetic series 7+15+.....+159, find (a) the number of terms n (b) the 5th term T(5) (c) the sum of the series S(n) 4. (a) Solve sinθ = 1 for 0°< θ°< 360°. (b) Solve 3tanθ - √3 =0 for 0°< θ°< 360°. 更新: 可否詳細的.....還有沒有其他人識計呀?????

最佳解答:

1. no figure is shown 2.10/sin800° = AC/sin 35° AC = 10sin 35°/sin80° = 5.82 cm 3. T(1) = 7 T(2)= 15 common difference d = 15 - 7 = 8 (a) Let n = no. of terms, 7 +(n-1)d = 159 7 + 8 x (n - 1) = 159 7 + 8n - 8 = 159 8n = 160 n = 20 (b) T(5) = 7+(5-1) x 8 = 39 (c) Sum = (T(1) + T(20)) x n /2 = (7 + 159) x 20 / 2 = 1600 4. (a) sinθ = 1 θ = 90° (b) 3tanθ - √3 =0 tanθ - 1/ √3 =0 tanθ = 1/ √3 θ = 60°or 240°