Trig Help

madchronic

madchronic

Member
Hey I usually never do this but this problem is bugging the shit out of me.

Can anyone post how to get

cos [sin^(-1)(2/3)+2 sin^(-1)(-1/3)]

I believe it's basically asking for cos(a+2b) but I can't get to the right answer

((8 sqrt(2))/27+(7 sqrt(5))/27)
 
13741339:DirtYStylE said:
Trigg and proffs are the cancer and aids of math. I will not help you with this. Sorry, not sorry.

You should try this instead of ns: wolframalpha.com
Click to expand...

I know haha. I don't have wolfram alpha pro so it only gives the answer not the actual steps.
 
13741391:madchronic said:
The answer is

((8 sqrt(2))/27+(7 sqrt(5))/27)

I just don't know how to get that
Click to expand...

wow it's been a lot longer than I thought than. Sorry, I don't think my trig skills are up to date
 
13741393:Iraq_Lobster said:
wow it's been a lot longer than I thought than. Sorry, I don't think my trig skills are up to date
Click to expand...

All good. It's not your average trig, my teacher pulls crazy questions from princeton,stanford, etc.
 
Are you allowed to use your graphing calculator or do you need to do it all by hand? if you start from the inside out you can start with sin^-1(2/3) is sin(x) = 2/3 solve for x basically, same with the -1/3. Assuming you're allowed your graphing calculator that gives you: sin^-1(2/3) = .72972766 rads. sin^-1(-1/3) = -.33983691 rads. .72972755 + 2(-.33983691) = .05005384. take the cos() of that and you'll get ((8 sqrt(2))/27+(7 sqrt(5))/27) in decimal form which is .99874757. If you need to solve it by hand without using the inverse sin function button on your calculator then your highschool trig is harder than college level trig... hope that helps!
 
13741931:LJ said:
Are you allowed to use your graphing calculator or do you need to do it all by hand? if you start from the inside out you can start with sin^-1(2/3) is sin(x) = 2/3 solve for x basically, same with the -1/3. Assuming you're allowed your graphing calculator that gives you: sin^-1(2/3) = .72972766 rads. sin^-1(-1/3) = -.33983691 rads. .72972755 + 2(-.33983691) = .05005384. take the cos() of that and you'll get ((8 sqrt(2))/27+(7 sqrt(5))/27) in decimal form which is .99874757. If you need to solve it by hand without using the inverse sin function button on your calculator then your highschool trig is harder than college level trig... hope that helps!
Click to expand...

When LJ is a math wizard and a ski god

giphy.gif
 
323191.image0.png


Hope this helps, op

First, I would use any rules you know to break up the identites and then pull it all apart using the laws above.

i have an exam rn ill do it after if i have time and nobody ele has done it

goodluck
 
You must log in or register to reply here.
Back
Top