ShmoopTube

Where Monty Python meets your 10th grade teacher.

Search Thousands of Shmoop Videos


ACT Math Videos 164 videos

Inequalities in Number Lines
3229 Views

ACT Math: Coordinate Geometry Drill 1, Problem 1. Which inequality is expressed by the number line?

ACT Math 3.1 Intermediate Algebra
1955 Views

ACT Math: Intermediate Algebra: Drill 3, Problem 1. Find the fifth number in the series.

ACT Math 3.1 Plane Geometry
2559 Views

ACT Math: Plane Geometry Drill 3, Problem 1. What is the area of the trapezoid shape in the video?

See All

ACT Math 3.2 Trigonometry 218 Views


Share It!


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.

Related Videos

Inequalities in Number Lines
3229 Views

ACT Math: Coordinate Geometry Drill 1, Problem 1. Which inequality is expressed by the number line?

ACT Math 3.1 Intermediate Algebra
1955 Views

ACT Math: Intermediate Algebra: Drill 3, Problem 1. Find the fifth number in the series.

ACT Math 3.1 Plane Geometry
2559 Views

ACT Math: Plane Geometry Drill 3, Problem 1. What is the area of the trapezoid shape in the video?

Surface Area of Cylinders
14741 Views

Haven't you always wondered how much cardboard it takes to encase a trunk warmer for your pet elephant?

Perimeter of Irregular Shapes
4864 Views

Want to figure out the area and perimeter of irregular shapes? Break them down into regular shapes. For example, a flower can be broken down into s...