need help with a tangent and normal question (1 Viewer)

[bedpotato]

rly..am i subbing wrong?

If you rationalise the denominator, you will get (sqrt2)/8. Is that what you're trying to get?

 

[ymcaec]

rly..am i subbing wrong?

Subbing x = 4:
1/ sqrt(2*4) - 4 / sqrt (2*4)^3
= 1/ 2sqrt2 - 4 / 16sqrt2
= 1/ 2sqrt2 - 1/4sqrt2
= 2/ 4sqrt2 - 1/4sqrt2
= 1/ 4sqrt2

complicated :/

 

[ymcaec]

For mentality A, line 3 shouldn't it be x^1+1/2? Isn't the power of 1/square root x = -1/2?

no because it is division
divide means subtract the powers

but y should be x^1/2 / sqrt 2

 

[Menomaths]

no because it is division
divide means subtract the powers

but y should be x^1/2 / sqrt 2

1-(-1/2) = 1+1/2

 

[ymcaec]

1-(-1/2) = 1+1/2

If u bring the x^1/2 up
the top part becomes x * x^-1/2
using index laws: x* x^-1/2 = x^(1+ (-1/2)) = x^1/2

index law with division states: x^a / x^b = x^(a-b)

 

[Menomaths]

If u bring the x^1/2 up
the top part becomes x * x^-1/2
using index laws: x* x^-1/2 = x^(1+ (-1/2)) = x^1/2

index law with division states: x^a / x^b = x^(a-b)

Ah, my bad

 

[bedpotato]

such a complicated pathway would only provide u misery, so we must look for another way to approach this question

The golden rule for all differentiating or integrating question: simplify the question so that it can be easily differentiated or integrated

MENTALITY (A)



MENTALITY (B)



This is attractive function can be easily differentiated

Mentality A, line 3: 1- 1/2 is 1/2. Not -1/2?
Same for Mentality B, line 4. 1 + (-1/2) = 1 - 1/2 = 1/2

You did it right when you were answering the question at the beginning. Just though I'd let you know, might become confusing.

 

[girlworld_club]

Subbing x = 4:
1/ sqrt(2*4) - 4 / sqrt (2*4)^3
= 1/ 2sqrt2 - 4 / 16sqrt2
= 1/ 2sqrt2 - 1/4sqrt2
= 2/ 4sqrt2 - 1/4sqrt2
= 1/ 4sqrt2

complicated :/

shouldn't it be 4/ 16 sqrt32

as 2 x 4 ^3 = 512

but you're right, thanks it does work out with a bit of tweaking.

 

[ymcaec]

shouldn't it be 4/ 16 sqrt32

as 2 x 4 ^3 = 512

but you're right, thanks it does work out with a bit of tweaking.

when you take out the 16 you forgot to square root it
sqrt 512
= sqrt (16 * 32)
= 4 sqrt 32
= 16 sqrt 2

 

[HeroicPandas]

Mentality A, line 3: 1- 1/2 is 1/2. Not -1/2?
Same for Mentality B, line 4. 1 + (-1/2) = 1 - 1/2 = 1/2

You did it right when you were answering the question at the beginning. Just though I'd let you know, might become confusing.

thanks boss!

 

[JT145]

Which one is the actual answer

having read through the thread I think we can establish that the book's answer is wrong?

 

[nerdasdasd]

Which one is the actual answer

having read through the thread I think we can establish that the book's answer is wrong?

What book?

 

[HeroicPandas]

Which one is the actual answer

having read through the thread I think we can establish that the book's answer is wrong?

u can just try it urself, its not even hard