Sin+Cos Question makes no sense to me

[College_Noobie]

Using a graph format in excel, plot the following function;
Y=2SinӨ + 3CosӨ

for values of Ө between 0 and 90?. From the graph find;
a.the maximum amplitude of the function.
2.A value of Ө which satisfies the equation
2SinӨ + 3CosӨ = 3.5

As evidence, you are required to show what formula you have used to produce the graph.

-
ok well.. i put 2 in sin, and 3 in cos
and did them added together to give a value, and tryed to make a graph..
i don't get the question, or what I am ment to do, or anything. please could someone help explain or give asmuch help as possible.

 

[symbolipoint]

Why must you use Excel? Are you permitted to use any graphing software program? If Excel contains trigonometric functions, you might be able to use
something like =2*sin(x)+3*cos(x) for the "formula".

 

[berkeman]

You need to make your first column the theta argument to the function. Put 0 in the first cell (call it A1), and in the second cell A2, put =A1+(90/100). Then click drag the second cell down to row 91, and use Ctrl-D to fill down that equation. That will give you a column for theta that varies from 0 to 90 in 1% increments.

Then the second column should be your Y formula, with the arguments for the sin() and cos() being the cell just to the left. Does that make sense? So you end up with two columns, theta and Y(theta) = 2sin(theta)+3cos(theta). Then use the chart wizard or whatever to make an x-y scatter chart that plots Y(theta), with theta as the horizontal axis, and Y(theta) as the vertical axis.

Does that get you back on track?

 

[berkeman]

BTW, it would be good to double-check the default in Excel to see if the argument to sin() and cos() is assumed to be in degrees, like we are using so far in this thread. If the default is assumed to be radians, then you'll need to include the conversion in your formula for Y(theta).

 

[College_Noobie]

need to get the answer in degree's
but excels degree's function seams to not be working as it should. also I am unable to determin if its ment to be fluctuating up and down or not.
any idea's?

also

That will give you a column for theta that varies from 0 to 90 in 1% increments

erm it goes up at 0.9 values, so highest value is 81.. so its not 1% increasments, please explain

-also current problem.. I am finding it impossible to convert it to degree's. me and others have tryed converting it using the dregee's function in excel, and radius*(180/Pi)
but doesn't give the answer I am suppose to get.

____|0|_10___|_20__
2Sin_|0|0.3473|_0.684
3Cos|2|_2.954_|_2.82
y___|2|_3.3___|_3.5

there is an attempt of a table of what it is ment to look like I've been told.
if don't understand table please ask and i will try and explain, but tbh i don't understand how they got those answers.

 

[TheoMcCloskey]

Excel expects trig arguments in radians. To use degress, convert the degrees to radians with Excel's RADIANS() function ,eg SIN(RADIANS(a1))

 

[berkeman]

erm it goes up at 0.9 values, so highest value is 81.. so its not 1% increasments, please explain

Ah, good point. I should have said to fill down to 101, to get all 100 steps at 1% increments.

 

[College_Noobie]

ThoMcCloskey please read what you put compared to what i put.

Excel expects trig arguments in radians. To use degress, convert the degrees to radians with Excel's RADIANS() function ,eg SIN(RADIANS(a1))

ok how will converting degree's which i need it to be in.. to a radius, which I am guessing it is as defult at the moment. going to help?
please read what i put.

need to get the answer in degree's
but excels degree's function seams to not be working as it should.

-also current problem.. I am finding it impossible to convert it to degree's. me and others have tryed converting it using the dregee's function in excel, and radius*(180/Pi)
but doesn't give the answer I am suppose to get.

{
____|0|_10___|_20__
2Sin_|0|0.3473|_0.684
3Cos|2|_2.954_|_2.82
y___|2|_3.3___|_3.5

}
there is an attempt of a table of what it is ment to look like I've been told.
if don't understand table please ask and i will try and explain, but tbh i don't understand how they got those answers.

 

[TheoMcCloskey]

Well, I guess I don't understand what you mean or want. I was trying to suggest how to get the proper values for sin(\theta) and cos(\theta) when \theta is expressed in degrees using Excel.

What are you trying to convert to degrees?

To plot the graph in Excel, simply construct the column of theta values (in degrees) as berkeman suggested. Then, construct another column with the expression you posted (Y) using the theta column and the radians conversion function (as I tried to suggest) so that you get the correct values of Y.

Now plot the values of the expression (Y) against the values of theta (in degrees) and read the graph relative to theta (in degrees) to get your answers.

P.S. - I don't understand your table.

 

[berkeman]

Well, I guess I don't understand what you mean or want. I was trying to suggest how to get the proper values for sin(\theta) and cos(\theta) when \theta is expressed in degrees using Excel.

What are you trying to convert to degrees?

To plot the graph in Excel, simply construct the column of theta values (in degrees) as berkeman suggested. Then, construct another column with the expression you posted (Y) using the theta column and the radians conversion function (as I tried to suggest) so that you get the correct values of Y.

Now plot the values of the expression (Y) against the values of theta (in degrees) and read the graph relative to theta (in degrees) to get your answers.

P.S. - I don't understand your table.

College -- Did Theo's help solve your problem? Theo's advice was pretty clear.

 

[College_Noobie]

my mates been able to work out a function to work out the degree's, which is as follows
=DEGREES(RADIANS(SIN(RADIANS(A1))*2)+RADIANS(COS(RADIANS(A1))*3))
im hopeing is right and I am going to try implment it now =)

using excels radians function degree's function didnt seam to work.

btw I am now 100% confused about radius and degree's and no idea what I am doing =) just woke up, but guna have a go.
p.s. sorry for seaming rude eirler

edit.
ive had ago, and this is what I've got
http://www.freewebs.com/rage_extreme/Sin%20Cos.xls
you reckon this is correct?