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ACT Math 3.2 Trigonometry 218 Views


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Description:

ACT Math: Trigonometry Drill 3, Problem 2. What is the value for side DF on this triangle?

Language:
English Language

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...

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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