Why does my child get sin 30 = −0.988 on the calculator?
Your child works out a sine, cosine or tangent with the calculator in radians, so sin 30 comes out as −0.988 instead of 0.5.
Why children do it
Calculators can measure angles in degrees or in radians, a unit used in later maths, and some start in radians. In degrees, sin 30 is 0.5. Checking sin 30 before starting shows which mode it's in; the screen usually shows D or DEG for degrees.
How to help at home
Ask them to check their calculator: sin 30 should be 0.5. If it isn't, it's not in degrees.
The right way
Find x, to 1 decimal place.
- 6.9Opposite and hypotenuse: x = 12 × sin 35° = 6.88..., which is 6.9.
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