Either my math book is wrong or my calculator doesn't work

[bobsmith76]

This book says that sin of 45 degrees is .70

My calculator which is a TI 83 says it's .85, plus this website also says it's .85

http://www.coolmath.com/graphit/

Who is right?

 

[bobsmith76]

Ok, this website
http://web2.0calc.com/
gives me the answer .70, but I would still like to know why a TI 83 is wrong

 

[superg33k]

The books right. Your calculator is calculating it in Radians. Switch it to degree's and it\l give you the right answer.

 

[Dr. Seafood]

It's a units problem. $45^{\circ} = {\pi \over 4}$. Indeed $\sin 45^{\circ} \approx 0.707$, when the argument of sin is measured in degrees, but $\sin 45 \approx 0.85$ since the 45 here is measured in radians. You have to tell your calculator to use a different unit of angle measurement.

 

[TylerH]

Always remember, when you turn your calculator on, press "Mode" to make sure it's in the correct angle unit measurement. You should be in degrees, but if you're in precal or trig, you'll move to radians pretty quick. If you're in geometry, you'll stay with degrees, so you'll have to switch it back to degrees every time you reset it. When reset, it defaults to radians.

 

[uart]

This book says that sin of 45 degrees is .70

Also, be careful with your significant digits bobsmith, otherwise both answers are wrong. If you are going to write 2 significant digits then it has to be 0.71 :)

 

[TylerH]

Also, be careful with your significant digits bobsmith, otherwise both answers are wrong. If you are going to write 2 significant digits then it has to be 0.71 :)

LOL! But, I think he's in geometry, which is typically a sophomore class. Most high school kids don't learn sig. figs. until chemistry, because it's not expected of them until they get to a high level science class (like chemistry).