#20
Top 50 Mistake
Calculator set to radians instead of degrees
"The Mode Mishap"
The Mistake in Action
Find $\sin(30°)$
Wrong: $\sin(30) = -0.988...$
Why It Happens
The calculator is in radians mode (showing "RAD" or "R"), not degrees mode. The student enters 30, thinking degrees, but the calculator interprets it as 30 radians.
The Fix
Check your calculator display — you should see "DEG" or "D", not "RAD" or "R".
To change mode on Casio Classwiz:
- Press MENU
- Select Settings
- Select Angle Unit
- Choose Degree
Correct answer: $\sin(30°) = 0.5$
Quick check: You should know that $\sin(30°) = 0.5$ — if you get anything different, check your mode!
Spot the Mistake
Can you identify where this student went wrong?
Find $\sin(30°)$
$\sin(30) = -0.988$
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: