Maths Question 急

2009-06-07 11:50 pm

If 1/ tan 22° = tan(6θ- 40°), then θ = ?.

What is the answer?

Thank you!

更新1:

Another question A coin is biased so htat probability o getting a head is twicc that of getting a tail. When tossing the coin twice, fnd the probability of getting two heads. The answer is 4/9. How can I get the answer?

回答 (1)

豆漿

2009-06-08 12:03 am

✔ 最佳答案

1/ tan x 會變成 tan ( 90°-x)
所以
1/ tan 22° = tan(6θ- 40°)
tan 68° = tan ( 6θ- 40°)
6θ- 40° = 68°
θ = 18°

兩次都係heads 即係第一次係head 同埋第二次係head
兩件事同時發生的機率係兩件事發生的機率相乘
而每一次出head的機率係 2/(1+2) = 2/3
所以 P(two head) = (2/3)^2 = 4/9

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