Ijust need a confirmation that my answer is right? find side ac. round to the nearest hundredth. the angles are: angle a = 40°, angle c = 90°, and angle b = 50°. side ba (the hypotenuse) = 3 cm. i did this: cos40° = ac/3 3cos40° = ac ac = -2.08, but a length can't be negative am i doing something wrong? or do i just write 2.08? i can't remember.

Your procedure is perfect, you're fine, however, bear in mind that, in a calculator when plugging in values for some functions, specially trigonometric ones, if you tell it cos(40), and the calculator is in Radian mode, it thinks you meant cosine of 40 radian units, if you give it cos(40) and it's in Degree mode, it thinks you meant 40°, and 40 radians is hugely different than 40°.

so, make sure your calculator is in Degree mode, as you'd have guessed, it isn't.