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Profile: Reiko07
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User Name: Reiko07
Forum Rank: Member
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Joined: Tuesday, October 30, 2018
Last Visit: Wednesday, April 24, 2019 10:33:18 PM
Number of Posts: 382
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  Last 10 Posts
Topic: for a total of three times
Posted: Wednesday, April 24, 2019 10:13:54 PM
Thank you very much, DS. Dancing

My English is probably at CEFR A1 or A2 level.
Topic: arcsin x (pronunciation)
Posted: Wednesday, April 24, 2019 9:55:55 PM
thar wrote:
That isn't a formula, is it, so much as an equation?


I just found this:

Machin's formula (for which the derivation is straightforward) is:

π/4 = 4 arctan 1/5 – arctan 1/239.


Wikipedia, John Machin


My English is probably at CEFR A1 or A2 level.
Topic: for a total of three times
Posted: Wednesday, April 24, 2019 9:36:39 PM
Blodybeef wrote:
Quote:
Is for really necessary? Is the following sentence correct?


It sounds better with "for"

However, I would personally construct this sentence like this : "The price was raised seven times since 2012."


Eh? Think I suppose the "a total of seven times" in my sentence is adverbial.

My English is probably at CEFR A1 or A2 level.
Topic: for a total of three times
Posted: Wednesday, April 24, 2019 12:28:48 AM
Koh Elaine wrote:
“I received the cheques from Najib for a total of three times.

Drag0nspeaker wrote:
Hi!
It seems correct - except that it's just long and "wordy".

Is for really necessary? Is the following sentence correct?

The price has been raised a total of seven times since 2012. (Without for.)
(my original sentence)

My English is probably at CEFR A1 or A2 level.
Topic: arcsin x (pronunciation)
Posted: Tuesday, April 23, 2019 6:48:43 PM
Thank you all, Dancing

thar wrote:
That isn't a formula, is it, so much as an equation?

Serge Lang, the author of the acclaimed algebra text Algebra, called it a formula.

Here's my proof of the formula:

α := arctan 1/5.
tan α = 1/5.
tan 2α = 5/12.
tan 4α = 120/119.
tan (4α - π/4) = 1/239.
α < π/6 because 1/5 < tan π/6. Thus,
– π/2 < 4α - π/4 < π/2.
Hence,
4α - π/4 = arctan 1/239.
That is,
π/4 = 4 arctan 1/5 – arctan 1/239.


We can use this formula to show:
π ≈ 3.1415926.

My English is probably at CEFR A1 or A2 level.
Topic: arcsin x (pronunciation)
Posted: Tuesday, April 23, 2019 5:37:47 PM
thar wrote:
"sine to the minus one"

Thank very much, thar.

You might have taken sin⁻¹ x to mean (sin x)⁻¹. I mean:

sin⁻¹ x = arcsin x, not sin⁻¹ x = (sin x)⁻¹.

Some Japanese math teachers pronounce sin⁻¹ x as "inverse sine x".

My English is probably at CEFR A1 or A2 level.
Topic: arcsin x (pronunciation)
Posted: Tuesday, April 23, 2019 5:17:52 AM
(1) arcsin x (2) arccos x (3) arctan x

(4) sin⁻¹ x (5) cos⁻¹ x (6) tan⁻¹ x


How would you pronounce these expressions?

Example:

Prove the formula π/4 = 4 arctan 1/5 – arctan 1/239.



My English is probably at CEFR A1 or A2 level.
Topic: Look at the baby sleeping.
Posted: Monday, April 22, 2019 7:52:00 PM
Thanks a lot, thar. Dancing

My English is probably at CEFR A1 or A2 level.
Topic: Is the "nothing but + adjective" construction possible?
Posted: Monday, April 22, 2019 7:44:45 PM
Thanks a lot, DS. Dancing

My English is probably at CEFR A1 or A2 level.
Topic: Look at the baby sleeping.
Posted: Monday, April 22, 2019 2:06:08 AM
(1) Look at the sleeping baby.
[from a grammar book for Japanese learners of English]

(2) Look at the baby sleeping.

Is (1) natural? I think (2) is better.

My English is probably at CEFR A1 or A2 level.

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