Josh's Claim

Geometry Level 3

Josh claims that tan θ \tan{\theta} is undefined for any θ \theta such that sin θ = 1 b 2 a 2 + b 2 \sin{\theta} = \sqrt{1 - \dfrac{b^2}{a^2+b^2}} , where b = 0 b=0 .

Is Josh correct?

Yes Not enough information No

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1 solution

Akeel Howell
Feb 10, 2017

We have that sin θ = 1 b 2 a 2 + b 2 \sin{\theta} = \sqrt{1 - \dfrac{b^2}{a^2+b^2}} , and b = 0 b=0 . Therefore, sin θ \sin{\theta} is simply 1 = ± 1 \sqrt{1} = \pm1 .

When sin θ = 1 or 1 cos θ = 0 , and tan θ \sin{\theta} = 1 \space \text{ or } -1 \implies \cos{\theta} = 0, \space \text{ and } \tan{\theta} is undefined since tan θ = sin θ cos θ \tan{\theta} = \dfrac{\sin{\theta}}{\cos{\theta}} .

When a =0 then Here no information about 'a'

shyam upadhyay - 4 years, 4 months ago

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If a = 0 a=0 , then sin θ \sin{\theta} is undefined, and hence tan θ \tan{\theta} is also undefined.

Akeel Howell - 4 years, 4 months ago

Here b=0 if a=0 then 0/0 indertminate form will be occur then how can you evaluate 1 -0/0

shyam upadhyay - 4 years, 4 months ago

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That's exactly my point. If a = 0 a=0 , then sin θ \sin{\theta} is undefined, and hence tan θ \tan{\theta} is also undefined, as stated in the question.

Akeel Howell - 4 years, 4 months ago

sin@ define everywhere in R

shyam upadhyay - 4 years, 4 months ago

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Yes it is. But consider the value of sin θ \sin{\theta} where θ \theta \to \infty or θ \theta \to -\infty . You cannot determine such a value. It is simply between 1 -1 and 1 1 , inclusive. Therefore, it is not a defined value. Choosing a a and b b such that both are equal to zero will leave θ \theta in an indeterminate form and thus, the value of sin θ \sin{\theta} will be undefined.

Akeel Howell - 4 years, 4 months ago

1/0 is undefined or Infinite But 0/0 is indeterminate only but for 1/0 we can say it will be infinite.

shyam upadhyay - 4 years, 4 months ago

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Division by zero is indeed undefined but I'm afraid I'm not seeing a point here. If the "it" you are referring to is sin θ \sin{\theta} , then no it won't be infinite since this function is bounded between 1 -1 and 1 1 , inclusive θ \forall \space \theta . If by "it," you mean 1/0, then it is undefined (infinite), but this brings us right back to the point of the question.

Akeel Howell - 4 years, 4 months ago

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