Math Is Fun Forum

Peaches47

Member

Registered: 2008-02-17

Posts: 13

Using a calculator to slove the equation

Here we go again.   This is the question:

"Use a calculator to slove the equation on the interval [0,2pi). Round to the nearest hundredth.
sin 2x - sin x= 0

These are the choices of answers:

0, 1.05, 3.14, 5.24
0, 2.09, 3.14, 4.19
1.05, 3.14, 5.24
0, 2.09,4.19

Now on the other hand I solved a problem simuliar to the one above (tan x= 3.0)

The answer is  1.25, 4.39 (easy)

But the one above I have no clue how to begin to figure it out.

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Struggling Middle Aged Math Student

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: Using a calculator to slove the equation

Now just find the values of x that satisfy sinx = 0 and cosx = 1/2

Peaches47

Member

Registered: 2008-02-17

Posts: 13

Re: Using a calculator to slove the equation

Thank You, but...........

How do I find one of the answers above from  sin x = 0 cos x =1/2?

answers:
0,1.05,3.14,5.24 or
0,2.09,3.14,4.19 or
0,2.09,4.19        or
1.05, 3.14,5.24

My inverse function is not giving me anything that matches

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Struggling Middle Aged Math Student

luca-deltodesco

Member

Registered: 2006-05-05

Posts: 1,470

Re: Using a calculator to slove the equation

do you have your calculator set to radians? that is what the answers there are given as, although either way you should be getting 0 as an answer atlest, since whatever angle mode you are in, sin-1(0) is 0, and therefore 3.14 aswell since sin(pi) = sin(0)

Last edited by luca-deltodesco (2008-02-25 19:50:52)

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JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Using a calculator to slove the equation

There are two solutions for

and two for

for x ∈ [0,2π). Your calculator will only give you one solution for each, so you have to work out the other solutions yourself.

I don’t know what your calculator is like but you can also use Windows’ scientific calculator. Follow these steps:

(i) Start → Programs → Accessories → Calculator (or Start → Run, and type “calc”).

(ii) In the View menu, select “Scientific” and “Radians”.

(iii) To calculate, sin[sup]−1[/sup]0, key in “0”, tick the small box marked “Inv”, and press “sin”. To calculate the other one, key in “0.5”, make sure the small box marked “Inv” is still ticked, and press “cos”.

Peaches47

Member

Registered: 2008-02-17

Posts: 13

Re: Using a calculator to slove the equation

thanks for the in put

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Struggling Middle Aged Math Student