nenoyage
Answered

Find the best solutions to your questions at Westonci.ca, the premier Q&A platform with a community of knowledgeable experts. Explore our Q&A platform to find in-depth answers from a wide range of experts in different fields. Join our platform to connect with experts ready to provide precise answers to your questions in different areas.

You are given that cos(A)=−35, with A in Quadrant II, and cos(B)=817, with B in Quadrant I. Find cos(A−B). Give your answer as a fraction.

Sagot :

Expand cos(A - B) with the identity

cos(A - B) = cos(A) cos(B) + sin(A) sin(B)

A is in quadrant II, so sin(A) > 0, and B is in quadrant I, so sin(B) > 0. Using the Pythagorean identity, we get

cos²(A) + sin²(A) = 1   ⇒   sin(A) = + √(1 - (-3/5)²) = 4/5

cos²(B) + sin²(B) = 1   ⇒   sin(A) = + √(1 - (8/17)²) = 15/17

Then

cos(A - B) = (-3/5) × 8/17 + 4/5 × 15/17 = 36/85

cos (A - B) is 36/85

How to simply the identity

Expand cos(A - B) with the identity

You get, cos(A - B) = cos(A) cos(B) + sin(A) sin(B)

Since A is in quadrant II, so sin(A) > 0,

B is in quadrant I, so sin(B) > 0.

Using the Pythagorean identity, we get

cos²(A) + sin²(A) = 1  

Make sin A the subject of formula

[tex]sin(A)^{2}[/tex] =  ([tex]\sqrt{(1 - (-3/5}[/tex])²)

Find the square root of both sides, square root cancels square

[tex]sin A[/tex] = 4/5

Repeat the same for the second value

[tex]sin A^{2} = \sqrt{(1- 8/17)^2}[/tex]

[tex]sin A[/tex] = 15/17

Substitute values into cos(A - B)

cos(A - B) =  cos(A) cos(B) + sin(A) sin(B) = (-3/5) * 8/17 + 4/5 * 15/17

cos (A - B) = 36/85

Therefore, cos (A - B) is 36/85

Learn more about trigonometric identities here:

https://brainly.com/question/7331447

#SPJ1

Thank you for your visit. We are dedicated to helping you find the information you need, whenever you need it. Your visit means a lot to us. Don't hesitate to return for more reliable answers to any questions you may have. Discover more at Westonci.ca. Return for the latest expert answers and updates on various topics.