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∘.
有條數學唔識計…有無人識計呀???教下我
2007-12-05 8:02 pm
回答 (2)
2007-12-05 10:44 pm
✔ 最佳答案
1. no figure is shown2.10/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∘
2007-12-05 8:21 pm
1a)7cm
b)180/3=60
c)7x7=49
b)180/3=60
c)7x7=49
收錄日期: 2021-04-14 19:53:48
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