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C3 double angle formula help?

ththhtehetheege
(edited 12 years ago)
Original post by krazyk12
Hi guys i'm having extreme difficulty solving these questions.

Solve these equations for 0≤θ≤360

1) sin2θ - = cos2θ

2) sin2θ - 1 = cos2θ

3) 3cos θ/2 = 2 + cosθ

4) cosθ = 5sin θ/2 + 3

Thanks a lot in advance guys and please leave full working out. Appreciated


We aren't a "Do your homework for you" service. We'll give you hints, but we aren't going to start by giving you full solutions.

Do you have any thoughts on how to approach these questions? Have you tried rewriting cos(2theta) or sin(2theta) in your equations and seeing if that helps?
Reply 2
Avatar for Jarred
Jarred
18
Try rewriting the equations in a way so that there is only one type of trigonmetrical function in the equation, then you can solve it how you would normally.
(For example, if an equation had both cos and sin in it, rewrite it so that it only had one of cos, sin, or tan in it, they're solvable that way.)
Original post by krazyk12
The most useless information I've heard all day. That tops the list


Not really. The best you can get Do you own work, but if you want help we're more than glad to help.
Original post by krazyk12


Thanks a lot in advance guys and please leave full working out. Appreciated


what so you can just pretend you worked it all out and get a pat on the back off your teacher, taking liberties. can't see why anyone here would literally do your homework for you.
look in your notes/textbook and decipher the answers yourself (surely you have those or you get someone else to write those too)
Reply 5
Avatar for krazyk12
krazyk12
OP
Original post by mariejulian

Original post by mariejulian
what so you can just pretend you worked it all out and get a pat on the back off your teacher, taking liberties. can't see why anyone here would literally do your homework for you.
look in your notes/textbook and decipher the answers yourself (surely you have those or you get someone else to write those too)


That's the type of message that is so clear to everyone that you weren't loved by your parents.
Original post by krazyk12
That's the type of message that is so clear to everyone that you weren't loved by your parents.


oh yes because the subliminal messaging in my text is apparently so clear to top psychologists such as yourself who cant even do their own maths homework
Original post by krazyk12
That's the type of message that is so clear to everyone that you weren't loved by your parents.


dude, you need to read your text book !! these questions are not that hard if you expand them out correctly using the double angle formula.

I'll re iterate, we are not a homework service, we will give you hints but not answers.

my hint is my first line
Reply 8
Avatar for SonnyBeatle
SonnyBeatle
I've another query
cos^2 theta sin^2 theta
Why does this equal (according to my textbook)
1/4 sin^2 2theta
not
1/2 sin^2 2theta
(edited 11 years ago)
Reply 9
Avatar for TenOfThem
TenOfThem
18
Original post by SonnyBeatle
I've another query
cos^2 theta sin^2 theta
Why does this equal (according to my textbook)
1/4 sin^2 2theta
not
1/2 sin^2 2theta


because 1/2 squared is 1/4

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