A ladder’s max angle for safety is 75 degrees. How long of a ladder is needed to reach 90 ft high?

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30 сен 2024

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Комментарии : 40

@luillierstephane1463 3 месяца назад

SOH.CAH.TOA is as important as PEMDAS.

@terry_willis 3 месяца назад

Why did he leave out the numerical value of the sine 75 degrees (= .966.) . Seems simple but some students may have gotten lost at the very end of the solution. Every thing else is explained in great detail.

@gavindeane3670 3 месяца назад

Because sin 75⁰ is exact but 0.966 is an approximation. 0.966 is not the numerical value of sin 75⁰. Approximation is something you do at the end when you have a final answer, not while you're still in the process of calculating the final answer.

@terry_willis 3 месяца назад

@@gavindeane3670 Thanks for your reply. I agree. Your are correct. I was just suggesting that John show an approximation of sine 75 degrees ( like .966) for viewer to follow since John tends to go into great detail.

@gavindeane3670 3 месяца назад

@@terry_willisI think if you watch the video from around the 20 minute mark, he's clearly expecting his students to be using a calculator, and once he's rearranged the question to get x = 90 / sin(75⁰) that's what he's expecting people to calculate. I don't think he wants you to enter 90/0.966.

@leetucker9938 3 месяца назад

90 / sin [75] = 93.2

@Kudeghraw 3 месяца назад

94.8 feet. If you have 75 degrees on one angle, the other has to be 15 which gives you a 9:3 ratio on the sides. Scale the sides up to 90:30 to fit the ask. 90squared plus 30squared = ladderlength squared. 8100 + 900 = 9000 = 94.8 feet. I am happy being off by a foot and a half and not using a chalkboard.

@Kudeghraw 3 месяца назад

@@gramasamy88 It was an eyeball solution. 9 feet and 3 feet would be a realistic size of a normal ladder leaned against wall with an eyeballed 75/15 angle making up 90 of the 180 degrees made with the right triangle. Then I just scaled up to 90 feet to fit the ask which required multiplying 9 and 3 each by 10 and then squaring each of which they sum to 9000. Then a rough sq root of 9000 leaves 94.86 feet meaning in the field, on a jobsite, you know 95 feet is going to be enough to cover a 90 foot wall sloping 75 degrees down.

@tommosley2844 3 месяца назад

It should be called the Imhotep theorem, as Pythagoras and the Greeks received this information from ancient Kemetic Egyptians. The builders of the great pyramids.

@richardhole8429 3 месяца назад

East to answer. No 90 foot ladder can ever be safe. For the math problem, 90 / sin(75°)= 93.17

@RCSTILE Месяц назад

This latter is a death trap. You would need an overhead crane to raise it.

@deborahwhit9583 Месяц назад

I would guess around 90....without trying

@Warpedsmac 25 дней назад

Answer should be expressed in feet and inches not decimals of one foot. Go out and try to get a 93.17' ladder!!!!! That's a mathematician's answer A 95 or 100ft foot ladder is a better answer.

@russelllomando8460 3 месяца назад

got it 93.177 sin 75 = O/H = 90/X thanks for the fun

@vladnedelcu969 3 месяца назад

Feet don't belong in geometry

@gavindeane3670 3 месяца назад

It's one calculation. The units aren't a concern at all. It could be feet or parsecs or leagues angstroms or cubits or anything. It doesn't matter.

@abeonthehill166 3 месяца назад

90ft/ sin 75 degrees = 93.174856 ft ……..bottom of ladder is 24.115427 ft from bottom of ladder . In the UK the height ratio to length from wall is ; for every 4 up, there must be 1 away from wall ….4:1

@Anastasia-l2w3b 5 дней назад

75 from ground 75 from wall Should be stated at onset A straight object cannot possess an angle It must be relative to an edge

@vswr10 Месяц назад

As there is not maximun length limit >93.17'. Any angle bellow 75 degrees is safe.

@alastairgreen2077 Месяц назад

How long a ladder, not of a ladder. Try improving your knowledge of English grammar.

@phrankus2009 3 месяца назад

The answer is moot, bc 90 feet is 9 stories high. I do not think there is a ladder, that tall, that is not attached to a structure, such as a municipal water tower .. .. What do I win?

@tobingj 3 месяца назад

What if the ladder is against the leaning tower of Pisa. Lots of possible answers. 😁 I know he answers it.

@luillierstephane1463 3 месяца назад

Exactly what I found, 93.17.....

@BlackhawkPilot 3 месяца назад

Anyone in the trades knows ladder come in 5’ increments so the real world answer is 95’

@thomasharding1838 2 месяца назад

I have a 24 ft. and a 16 ft. ladder. But the real question that anyone in the trade would ask is, "How many people do we need to elevate a 93 foot ladder and who' gonna go up it? Maybe a long ladder truck from the Fire Department?"

@pamnetwork7787 2 месяца назад

Please make less descriptive video

@RblJ38 2 месяца назад

90 feet?? It's a fire engine ladder

@TheAZZA0990 3 месяца назад

93.18 feet - basic trig!! :o After stressing to read the problem - the composer doesn't?!! His answer of 93.17 is THE WRONG SIDE of the safety point!!! :o