A level Trigonometry Help
Express 4 sin x + 3 cos x in the form r sin (x + α). Hence find all the values of x in the range 0 ≤ x ≤ 360° for which cos 3x = cos 2x.
I‘ve done the first part, which I got 5 sin (x + 36.9°), but I have no idea how to solve the second part.
Can anyone help please, thanks!
I‘ve done the first part, which I got 5 sin (x + 36.9°), but I have no idea how to solve the second part.
Can anyone help please, thanks!
Scroll to see replies
Original post by mqb2766
I think they want you to.expand the multiple angles in terms of cos(x) and sin(x).
However, id just take acos directly and forget about the first part.
However, id just take acos directly and forget about the first part.
I‘ve tried to expand it in terms of cosx and sinx but I can’t link back to the first equation.
Cos(A+_B) = CosAcosB + SinASinB
Original post by charlenecsn
I‘ve tried to expand it in terms of cosx and sinx but I can’t link back to the first equation.
Can you upload?
Original post by CaptainDuckie
Cos(A+_B) = CosAcosB + SinASinB
I got 4cos^3(x)-3cos(x)=2cos^2x-1, but I can't relate this to the first equation.
Upload pic bro
Original post by mqb2766
Can you upload?
Cannot see that at all😂😂
Original post by CaptainDuckie
Cannot see that at all😂😂
you mean the pic cant be viewed?😂
Original post by charlenecsn
you mean the pic cant be viewed?😂
Your writing
Original post by CaptainDuckie
Your writing
Original post by charlenecsn
Will have a look in the morning, but the simple thing to do is take acos
to give
3x = +/-2x + 2*pi*n
Original post by mqb2766
Will have a look in the morning, but the simple thing to do is take acos
to give
3x = +/-2x + 2*pi*n
to give
3x = +/-2x + 2*pi*n
Alright, thank you so much!!!
Original post by simon0
As a side note, another method is to use the trigonometric sum-product results, specifically:
.
For this case: .
.
For this case: .
Thanks! ))but that formula isn't in the syllabus
Original post by CaptainDuckie
Cos(A+_B) = CosAcosB + SinASinB
Close but not quite.
Original post by simon0
Close but not quite.
It’s the Sin(A _B) = SinASinB - CosAcosB
( I realised )
But forgot to edit
(edited 3 years ago)
Quick Reply
Related discussions
- gcses
- Trapezium question - URGENT help needed!
- A Level maths
- Pre Uni gap year advice
- Is anyone studying Construction Project Management at Sheffield Hallam?
- Cambridge University Maths Additional Information
- aqa a level physics mechanics
- Maths A level - Trignometric proof
- A level subject choices
- Support
- preparation for first year engineering
- Careers
- edexcel ias chemistry p2
- Physics a level without maths a level
- What is the syllabus for the futher maths gcse this year?
- Advanced mathematics
- Maths yr2 trig help
- biochemistry access course help
- a* at a level maths
- Changing Math Tiers at the beginning of year 11
Latest
Trending
Last reply 3 days ago
Did Cambridge maths students find maths and further maths a level very easy?Last reply 2 weeks ago
Edexcel A Level Mathematics Paper 2 unofficial mark scheme correct me if wrongMaths
71
Trending
Last reply 3 days ago
Did Cambridge maths students find maths and further maths a level very easy?Last reply 2 weeks ago
Edexcel A Level Mathematics Paper 2 unofficial mark scheme correct me if wrongMaths
71
