Math Is Fun Forum

RickyOswaldIOW

Member

Registered: 2005-11-18

Posts: 212

Radian Mode

Does anyone know how I can switch my calculator to radian mode?  It's a Casio ƒx-83WA.

If no one can then maybe you can tell me if I've worked this out correctly?

(The image might not show up for a while, not sure why).

I need to work out the perimeter of the shaded area.
I started by taking the triangle and spliting it down the middle to make 2 right angled triangles, angle 0.8 and Hypotenuse 9 (call the triangle ABC where Hypotenuse is BC). 
AC = 9Sin0.8 = M

Therefore, the length of the chord from the image is 2M.  Since the arc is 1.6

2M+1.6 = Perimeter

I cannot find M since I cannot figure out how to put my calculator into radian mode but I looked at the answer at the back of the book.

2M+1.6 = 27.3
2M = 25.7
M = 12.85

I know from a previous example that 10Sin0.8 = 7.174 so I'm guessing that my answer is wrong because of the difference.

Last edited by rickyoswaldiow (2006-07-04 22:16:54)

---

Aloha Nui means Goodbye.

MathsIsFun

Administrator

Registered: 2005-01-21

Posts: 7,713

Re: Radian Mode

Good logic, and nearly right. You just forgot to multiply 1.6 by 9

The sine of 0.8 is 0.7173561... (when in trouble use our Scientific Calculator or Function Grapher and Calculator)

So the chord is 2 * 9 * 0.7173561 = 12.9124
And the arc is 9*1.6 = 14.4

So the total perimeter is 27.3124

---

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

RickyOswaldIOW

Member

Registered: 2005-11-18

Posts: 212

Re: Radian Mode

because the angle in radians is 1.6 when the radius is 1? I was unsure of this but thanks for pointing it out

Funny:

2M+1.6 = 27.3

Is this a coincidence?

Last edited by rickyoswaldiow (2006-07-05 05:56:47)

---

Aloha Nui means Goodbye.

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Radian Mode

just find "mode" button and press it.

---

X'(y-Xβ)=0

RickyOswaldIOW

Member

Registered: 2005-11-18

Posts: 212

Re: Radian Mode

Thanks George

For any with the same question, you need to press the mode button twice and radian mode is the second option there.  There are 3 pages of modes but I could not figure this out

---

Aloha Nui means Goodbye.

George,Y

Member

Registered: 2006-03-12

Posts: 1,379

Re: Radian Mode

If you need to get a result in emergency.
try this
x(rad)=180°x/Pi

or get a users manual click here

---

X'(y-Xβ)=0