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ACT Mathematics Videos 164 videos
ACT Math: Coordinate Geometry Drill 1, Problem 1. Which inequality is expressed by the number line?
ACT Math: Intermediate Algebra: Drill 3, Problem 1. Find the fifth number in the series.
ACT Math: Pre-Algebra Drill 1.2. What proportion of Jenna's day is spent Wii-swimming?
ACT Math 5.1 Pre-Algebra 466 Views
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Description:
ACT Math: Pre-Algebra Drill 5, Problem 1. Factoring in depreciation, how much is the car worth?
Transcript
- 00:02
And here is your shmoop de jour.
- 00:04
Simplified tangents squared alpha over sine squared alpha minus 1
- 00:10
And here are the potential answers...
- 00:14
Okay well whenever we see a tangent we can change
- 00:18
to sine over cosine. Now we have a triple layer fraction cake.
Full Transcript
- 00:23
To get rid of it, we multiply by one over sin squared alpha
- 00:28
The sines squared alpha cancels out on the top and bottom like this
- 00:31
which leaves us with one over cosine squared alpha -1
- 00:36
cosine and secant are inverse functions
- 00:39
so 1 over cosine squared alpha is the same thing
- 00:43
as secant squared alpha and the handy dandy trig identity
- 00:46
1 plus tangent squared alpha equals secant squared alpha
- 00:49
can be rearranged to become secant squared alpha -1
- 00:53
equals tangent squared alpha. What do you know? We're left with secant squared alpha
- 00:57
-1 in our expression
- 00:59
and we just figured out secant squared alpha -1 equals tangent squared alpha.
- 01:04
Which is option E.
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