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ACT Math 5.3 Trigonometry 218 Views
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Description:
ACT Math: Trigonometry Drill 5, Problem 3. What is the length of side x?
Transcript
- 00:02
Here's your shmoop du jour...
- 00:05
cos(A) = 3/7. What is the length of side x?
- 00:09
And here are your options...
- 00:14
Okay, so we know the cosine of angle A...
- 00:16
and we need to use it to find the length of side x...
Full Transcript
- 00:20
The cosine of an angle is equal to the adjacent side over the hypotenuse.
- 00:24
If the adjacent side is 3 and the hypotenuse is 7, we can use the Pythagorean theorem to
- 00:29
solve for the missing leg, x.
- 00:37
So we can just plug our numbers into this formula,
- 00:39
Three squared plus x squared equals seven squared.
- 00:43
9 plus x squared equals 49.
- 00:49
x squared equals 40.
- 00:53
x equals the square root of 40.
- 00:55
The square root of 40 is equal to 2 root 10, and there you have it...
- 00:59
...option C. That's the way to go.
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