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Right Triangles and Trigonometry Videos 37 videos
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Description:
ACT Math: Trigonometry Drill 3, Problem 2. What is the value for side DF on this triangle?
Transcript
- 00:02
Here's another shmoop du jour...
- 00:04
For the following right triangle DEF, E = 30° and EF = 15. What is DF?
- 00:14
And here are your potential answers...
- 00:19
Another 30-60-90 triangle question.
- 00:22
Hopefully we're seeing these things in our sleep by now...
Full Transcript
- 00:27
We know that the ratios of the sides in a 30-60-90 triangle are 1 to square root of 3 to 2...
- 00:34
...and we know that this line, DF, will be an index of 1... EF will be 2...
- 00:41
So we can make a simple ratio here where DF is to EF as 1 is to 2.
- 00:47
We are told that EF is 15... so 1 is to 2 as DF is to 15.
- 00:54
Now we just cross-multiply 15 times 1, like this... and set it equal to 2DF.
- 01:00
Then divide both sides by 2 and we have DF equals 7.5.
- 01:04
Answer A.
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