# Typo on Stage 3 ,Probabilities, 5.1

1. ### Au Yeung Yat Expand Collapse

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"The consideration above is exactly the same as the argument leading to the definition of expection in previous chapter. In fact,
E(X) = 10, 000, 000P(X = +10, 000, 000)− 5P(X = −5) ≈ −4.285

That is, if we play the game many times, we should expect to lost roughly \$4,285 per game. "
4.285=4,285 ?!

#1 Au Yeung Yat, 2015-08-13
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回覆 1# Au Yeung Yat

Apparently this is a typo. We will contact the maintainer of the question pool to follow up the case.

-- by Guo Xin

#2 56377379, 2015-08-14
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I have just got the reply that the figure has been updated accordingly.

-- by Guo Xin

#3 56377379, 2015-08-17
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Also,(Level 3 Complex Number, Ch.3 Theorem 3.3)
"Please be reminded again that, we are using radians(rad) as the measure unit for all angels and arguments."

#4 Au Yeung Yat, 2015-08-18
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回覆 4# Au Yeung Yat

Er... the sentence appears OK, right? What is your question?

-- by Guo Xin

#5 56377379, 2015-08-19
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回覆 5# Mathematics tutor 1

"...we are using radians(rad) as the measure unit for all angels and arguments."

#6 Au Yeung Yat, 2015-08-19
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回覆 6# Au Yeung Yat

Although I still am confused about your question, I guess what you asked is "how can radian be the measure of an angle?", is that correct?

Radian is used to measure the angle. There is no unit, and if used, the trigonometric functions enjoy good Taylor expansions. Approximately 1 rad equals 57.29578 degrees. For details, see the wikipedia page https://en.wikipedia.org/wiki/Radian, or some standard middle school mathematics textbooks.

-- by Guo Xin

#7 56377379, 2015-08-20
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本帖最後由 Au Yeung Yat 於 2015-8-29 00:18 編輯

回覆 7# Mathematics tutor 1
1 angle is NOT 1 angel

#8 Au Yeung Yat, 2015-08-29
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回覆 8# Au Yeung Yat

Thank you for the kind comment and your point is absolutely right. Let me forward the comment to the forum maintainer to follow up.

-- by Guo Xin

#9 56377379, 2015-08-29
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回覆 8# Au Yeung Yat

Typo reported and I got the reply from the Gifted Education Section that the typo will be fixed in the coming revision of content.

Many thanks for reporting.

-- by Guo Xin

#10 56377379, 2015-08-29