Math help

[another random person]

So I need to find the intercept between a straight line (y=14.5) and a cosine curve. I have attempted the eqn but unfortunately without success. I've attached an image of my working out below so please correct if you notice anything off with my algebra.

 

 

Thanks in advance

[Dash Lambda]

You made an error when multiplying by 621.

[another random person]

11 hours ago, Dash Lambda said:

You made an error when multiplying by 621.

How do i fix it?

[Dash Lambda]

1 minute ago, another random person said:

How do I fix it?

Look at your work.

I'll give you a hint: You have multiple terms.

[another random person]

7 minutes ago, Dash Lambda said:

Look at your work.

I'll give you a hint: You have multiple terms.

Oh right so I need to multiply the whole entire left side by 621 instead of just (22/69 *pi). 

But now my answer is 160.......and I know it should be around 4-5 or somewhere in the single digits.

[Dash Lambda]

6 minutes ago, another random person said:

Oh right so I need to multiply the whole entire left side by 621 instead of just (22/69 *pi). 

But now my answer is 160.......and I know it should be around 4-5 or somewhere in the single digits.

If you corrected it properly, it should read: x = 621(cos^-1(29/171) + 22π/69)/(100π)

Which evaluates to a reasonable value.

[another random person]

10 minutes ago, Dash Lambda said:

If you corrected it properly, it should read: x = 621(cos^-1(29/171) + 22π/69)/(100π)

Which evaluates to a reasonable value.

Yes, I corrected it to that but when I enter it into my calculator with all the correct bracket placements, it always gives the result of 160, regardless of what I do. I'm wondering if my calculator is unable to handle these forms of equations....because I tried an online calculator which gave the seemingly correct result of approx. 4.7.

 

https://www.symbolab.com/solver/algebra-calculator/\frac{621\left(\arccos\left(\frac{29}{171}\right)%2B\frac{22\pi}{69}\right)}{100\pi}%3Dx

[Dash Lambda]

1 minute ago, another random person said:

Yes, I corrected it to that but when I enter it into my calculator with all the correct bracket placements, it always gives the result of 160, regardless of what I do. I'm wondering if my calculator is unable to handle these forms of equations....because I tried an online calculator which gave the seemingly correct result of approx. 4.7.

 

https://www.symbolab.com/solver/algebra-calculator/\frac{621\left(\arccos\left(\frac{29}{171}\right)%2B\frac{22\pi}{69}\right)}{100\pi}%3Dx

What calculator do you have?

[another random person]

Just now, Dash Lambda said:

What calculator do you have?

Just the basic Casio fx-100 AU plus. I will be pretty triggered if the calculator is causing issues.

[Dash Lambda]

25 minutes ago, another random person said:

Just the basic Casio fx-100 AU plus. I will be pretty triggered if the calculator is causing issues.

Your calculator is set to degrees.

[another random person]

1 minute ago, Dash Lambda said:

Your calculator is set to degrees.

What should it be set to?

[Dash Lambda]

15 minutes ago, another random person said:

What should it be set to?

Radians.

Radians are the fundamental measure of angle that actually works, degrees are just a modification that makes it easier to say. 

[another random person]

Just now, Dash Lambda said:

Radians.

Radians are the fundamental measure of angle that actually works, degrees are just a modification that makes it easier to say. 

Oh! Thanks heaps!! You're a life saver.