For positive acute angles
1 answer:
9514 1404 393
Answer:
77/85
Step-by-step explanation:
<u>Given</u>:
cos(A) = 4/5
sin(B) = 15/17
<u>Find</u>:
cos(A-B)
<u>Solution</u>:
From your knowledge of Pythagorean triples, you know that one of them is (3, 4, 5) and another is (8, 15, 17). Using your imagination, or by drawing the triangles, you can determine the needed trig functions to be ...
sin(A) = 3/5
cos(B) = 8/17
__
Alternatively, you can use the Pythagorean identity to find ...
sin(A) = √(1 -cos²(A)) = √(1 -(4/5)²) = √(9/25) = 3/5
cos(B) = √(1 -sin²(B)) = √(1 -(15/17)²) = √(64/289) = 8/17
__
Then application of the angle difference formula is straightforward.
cos(A -B) = cos(A)cos(B) +sin(A)sin(B)
cos(A -B) = (4/5)(8/17) +(3/5)(15/17) = (32 +45)/85
cos(A -B) = 77/85
_____
Some graphing calculators can express the result ...
cos(arccos(4/5) -arcsin(15/17)) ≈ 0.90588235294
... as the fraction 77/85
You might be interested in
You can find the coordinates of any graph by using a coordinate table, which looks as so in the chart provided below.
What you do is you, put in the letter x and then put what y is equal to in the second box. You plug in any number for x and you solve in order to find the y coordinate. Once you do, for example for plugging in -1 into x you get 1. So your coordinate would be (-1,1).
What you do is you, put in the letter x and then put what y is equal to in the second box. You plug in any number for x and you solve in order to find the y coordinate. Once you do, for example for plugging in -1 into x you get 1. So your coordinate would be (-1,1).