the trig DAT thread

[jdmsamurai]

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for some reason i hate trig on the QR section...and i keep getting stuck on some of the problems...so if you can share your problems and solutions that would be great...or post problems for other to solve

here is one that caught my attention on achiever

sin^2(t)(1 + tan^2(t)) =
(t stands for theta)

the answer is tan^2(t)

can anyone explain?

 

[BodybldgDoc]

for some reason i hate trig on the QR section...and i keep getting stuck on some of the problems...so if you can share your problems and solutions that would be great...or post problems for other to solve

here is one that caught my attention on achiever

sin^2(t)(1 + tan^2(t)) =
(t stands for theta)

the answer is tan^2(t)

can anyone explain?

sin^2(t)(1+tan^2(t))= Sin^2(t) * (Sec^2(t)) as 1+tan^2(t)=Sec^2(t)
= Sin^2(t) * (1/Cos^(t)) as Sec^2(t)= 1/Cos^2(t)
=Sin^2(t)/Cos^2(t)
=tan^2(t)

 

[jdmsamurai]

ahhh that explains thats....

do you know how to solve the equivalence things also like

what is the same as cos(pi/6)?...how would one go about solving that?

 

[BodybldgDoc]

ahhh that explains thats....

do you know how to solve the equivalence things also like

what is the same as cos(pi/6)?...how would one go about solving that?

cos(pi/6)= cos(pi/6) * 180/pi = Cos 30
You can figure out what the fractional value for Cos 30 is from the trignometric value table that takes like 2 minutes to write up.

 

[jdmsamurai]

where can one go find this trignometric value table?

 

[BodybldgDoc]

http://www.easycalculation.com/area/trigonometry-tables.php

 

[Streetwolf]

ahhh that explains thats....

do you know how to solve the equivalence things also like

what is the same as cos(pi/6)?...how would one go about solving that?

If you have cos(x), then you only need to consider the following values of x:

x, pi-x, pi+x, 2pi-x.

So for pi/6, you have:

pi/6, pi-(pi/6) = 5pi/6, pi+(pi/6) = 7pi/6, and 2pi-(pi/6) = 11pi/6

Your values are pi/6, 5pi/6, 7pi/6, and 11pi/6. Now you need to figure out which ones are equivalent. Remember that for sin values you look at the y axis and cos values are the x axis. Equivalent sin values will be anything between 0 and pi, or anything between pi and 2pi (in the former all are positive, in the latter all are negative). This is just dividing the circle into top and bottom halves. Equivalent cos values will be anything between pi/2 and 3pi/2 or between (0 and pi/2) or (3pi/2 and 2pi). This is just dividing the circle into left and right halves.

Example: For cos(pi/6) I listed the 4 possible equivalent values above. This is a cos problem with pi/6. We know pi/6 fits into the latter case above: it is either between 0 and pi/2, or between 3pi/2 and 2pi. So of 5pi/6, 7pi/6, and 11pi/6, only 11pi/6 is between (0 and pi/2) or (3pi/2 and 2pi). The other two are between pi/2 and 3pi/2. So cos(11pi/6) is equivalent to cos(pi/6).