What is 9 and 10? what's the corect answer?

9. C, because subtracting a negative number "changes" the sign to +
10. C, for the same reason.  The equation could be rewritten as -4.2+6.9, which equals 2.7

Hello! i hope this
since the cosine is the ratio of the adjacent side to the hypotenuse, you can see that cos 60° = ½. answer. according to the property of cofunctions (topic 3), sin 30° is equal to cos 60°. sin 30° = ½.

All you have to do is multiply