f.4 maths (20點)

👨🏻‍🏫 學術台數學

匿名

2011-05-22 6:02 pm

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please help me ... thank you

更新1:

(a)我唔明點解係-√3cosϑ/2 (b)答案係2√3 / 3tanϑ

回答 (1)

myisland8132

2011-05-22 6:37 pm

✔ 最佳答案

(a) 3cos150sin(90 + ϑ) + tan240cos(360 - ϑ)

= -3cos30cosϑ + tan60cosϑ

= -3(√3/2)cosϑ + √3cosϑ

= -√3cosϑ/2

(b) tan150/tan(-ϑ) + cos180tan(90 + ϑ)/tan60

= tan30/tanϑ + 1/(√3cotϑ)

= 1/(√3tanϑ) + 1/(√3cotϑ)

= √3/(3sinϑcosϑ)

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