- #1

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Sin(90°-θ)

What does it mean?

I know what Sin θ is and I know that Sin 90° = 1.

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- Thread starter Feodalherren
- Start date

- #1

- 603

- 6

Sin(90°-θ)

What does it mean?

I know what Sin θ is and I know that Sin 90° = 1.

- #2

- 603

- 6

Just in case it's important, Sin θ=

(2x)(9+4x^2)^(1/2) / (9+4x^2)

(2x)(9+4x^2)^(1/2) / (9+4x^2)

- #3

ehild

Homework Helper

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Do you know how sin(90°-θ) is related to cos(θ)?

What is the full problem?

ehild

What is the full problem?

ehild

- #4

Mentallic

Homework Helper

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Sin(90°-θ)

What does it mean?

I know what Sin θ is and I know that Sin 90° = 1.

θ is some angle (we'll only deal with acute angles here) and then sin θ is the ratio of the opposite side to the hypotenuse in a right-angled triangle with one of its angles as θ. But if you look at that same triangle, you can deduce that the last angle must be

180° - 90° - θ = 90° - θ

because a triangle's angles add up to 180

And now, what is the cosine of that angle? That is, what is cos (90° - θ)? Well, since cos of an angle is the ratio between the adjacent side and the hypotenuse, these are exactly the same sides in the ratio of sin θ, so that means that sin θ = cos (90° - θ)

Can you use a similar procedure to find out what Sin(90°-θ) is?

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