View Full Version : More Math, this time, PreCalculus.
Goldenboko
01-14-2009, 12:42 PM
Okay, a question on a test I'm going to take today reads something like Simplify the following =
tan325-tan25
1-tan325tan25
I'd just go:
tan(325-25)
tan300
And that'd be the answer right?
qwertysaur
01-14-2009, 02:58 PM
You can go further than that Boko.
From tan(300) you can break it into sin(300)/cos(300)
sin(300) = -sin(60) = √(3)/2
cos(300) = cos(60) = 1/2
So you get (-√(3)/2)/(1/2) = -√(3)
You can remember that tan(60) = √(3) and skip the sin and cos stuff
. Just remember 300 is in quadrant IV so sin and tan is negative. cos is positive in quadrant IV. :p
blackmage_nuke
01-14-2009, 03:08 PM
Okay, a question on a test I'm going to take today reads something like Simplify the following =
tan325-tan25
1-tan325tan25
I'd just go:
tan(325-25)
tan300
And that'd be the answer right?
Wait!!! For that to work wouldnt it have to be
tanA - tanB
1 + tanAtanB
emphasis on the +
So for your problem I would first change all the tan's into sin/cos
So up the top we get
sin325/cos325 - sin25/cos25
which simplifies to
(sin325cos25-sin25cos325) / cos325cos25
then becoming
(sin 325-25) / cos325cos25
and thus
(sin 300) / cos325cos25 (part1)
down the bottom we get
1 - (sin325sin25) / (cos325cos25)
Which converts to
(cos325cos25 - sin325sin25) / (cos325cos25)
making cos(325 + 25) / (cos325cos25)
making cos(350) / (cos325cos25) (part2)
and so when we put part 1 over part 2 the cos325cos25 cancels leaving us with
sin(300)/cos(350)
From there sin300 can be made into -sin60 as sin is negative in the 4th quadrant and cos350 can be made cos10 as cos is positive in the 4th quadrant
-sin60 = -sqrt3/2
so we get to
(-sqrt3) / 2cos10
I dont know what to do about cos 10
Of course if that initial - was a typo Ive just wasted precious minutes in which case i advise that in the future you shouldnt be so negative hohoho pun!!
Goldenboko
01-14-2009, 08:11 PM
You can go further than that Boko.
From tan(300) you can break it into sin(300)/cos(300)
sin(300) = -sin(60) = √(3)/2
cos(300) = cos(60) = 1/2
So you get (-√(3)/2)/(1/2) = -√(3)
You can remember that tan(60) = √(3) and skip the sin and cos stuff
. Just remember 300 is in quadrant IV so sin and tan is negative. cos is positive in quadrant IV. :p
I accidentally reversed that on the test... and got √(3)/3 instead of just √(3).
Dammit. ;-;
Powered by vBulletin® Version 4.2.3 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.