# Trigonometric Functions help

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#1
Hi

I'm trying to learn trigonometric functions,

The question is to:

express 4.sin(Ωt+1.2°) in the form of a.sin(Ωt) ± b.cos(Ωt)

I wanna use an argand diagram to verify my answer

Thanks!
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6 years ago
#2
What is the question?
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#3
(Original post by poorform)
What is the question?
express 4.sin(Ωt+1.2°) in the form of a.sin(Ωt) ± b.cos(Ωt)
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#4
(Original post by dc2209)
express 4.sin(Ωt+1.2°) in the form of a.sin(Ωt) ± b.cos(Ωt)
using compound angle formula
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6 years ago
#5
Are you familiar with the addition formulae for trigonometric functions?
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#6
(Original post by razzor)
Are you familiar with the addition formulae for trigonometric functions?
nope
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6 years ago
#7

sin(A+B) = sin(A)cos(B) + sin(B)cos(A)
sin(A-B) = sin(A)cos(B) - sin(B)cos(A)

cos(A+B) = cos(A)cos(B) - sin(A)sin(B)
cos(A-B) = cos(A)cos(B) + sin(A)sin(B)
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#8
(Original post by razzor)

sin(A+B) = sin(A)cos(B) + sin(B)cos(A)
sin(A-B) = sin(A)cos(B) - sin(B)cos(A)

cos(A+B) = cos(A)cos(B) - sin(A)sin(B)
cos(A-B) = cos(A)cos(B) + sin(A)sin(B)
yes that is the compound angle formula i mentioned
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6 years ago
#9
So substitute the appropriate values into the formula for sin(A+B) and see what you get. Compare it with a.sin(Ωt) ± b.cos(Ωt).
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#10
(Original post by razzor)
So substitute the appropriate values into the formula for sin(A+B) and see what you get. Compare it with a.sin(Ωt) ± b.cos(Ωt).
Ok so 4[sin+Ωt] x cos1.2 + cosΩt x sin 1.2]
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6 years ago
#11
(Original post by dc2209)
Ok so 4[sin+Ωt] x cos1.2 + cosΩt x sin 1.2]
"sin+Ωt" doesn't mean anything. You can't have sine plus an angle.
Also, I don't why you put another squared bracket after the Ωt. The 4 needs to multiply the whole thing.
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6 years ago
#12
[QUOTE=dc2209;57214085]Hi

I'm trying to learn trigonometric functions,

The question is to:

express 4.sin(Ωt+1.2°) in the form of a.sin(Ωt) ± b.cos(Ωt)

Hello. I have attahced a solution below. If you obtain a copy of the Edexcel A Level Mathematics core 3 syllabus, it explains how to undertake Trig questions like yours, using compound angle formulae. It is a compound angle as A is not the same as B. If A was the same as B, then it would be Double Angle Formulae.

As for an Argand Diagram, these are used in conjunction with Complex Numbers, which are part of the Edexcel Further Pure 1 syllabus.

For further help and support on Trig Identities, please visit Exam Solutions.net or www.m4ths.com.

Thanks
Vandomo
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#13
[QUOTE=van.domo;57379937]
(Original post by dc2209)
Hi

I'm trying to learn trigonometric functions,

The question is to:

express 4.sin(Ωt+1.2°) in the form of a.sin(Ωt) ± b.cos(Ωt)

Hello. I have attahced a solution below. If you obtain a copy of the Edexcel A Level Mathematics core 3 syllabus, it explains how to undertake Trig questions like yours, using compound angle formulae. It is a compound angle as A is not the same as B. If A was the same as B, then it would be Double Angle Formulae.

As for an Argand Diagram, these are used in conjunction with Complex Numbers, which are part of the Edexcel Further Pure 1 syllabus.

For further help and support on Trig Identities, please visit Exam Solutions.net or www.m4ths.com.

Thanks
Vandomo

Ah thanks, that makes sense.

in my notes I have d = tan^(-1) 0.083/3.996 = (this should be 2 degrees), is this for construction of the argand diagram?
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