Hey there! I'm happy to help!
To find this other side given an angle and a side, we will use a trigonometric function. The three basic ones are sine, cosine, and tangent. You can remember these and what what they are using the mnemonic "soh cah toa".
SOH: Sine= Opposite/Hypotenuse
CAH: Cosine= Adjacent/Hypotenuse
TOA: Tangent= Opposite/Adjacent
We see that the sides involved are the opposite and hypotenuse.
Therefore, we can write this equation.
sin40= w/28
We multiply both sides by 28 to isolate the w.
28×sin40=w
Now, we find the sine of 40 on our calculator and then we multiply it by 28.
w≈18
Therefore, the answer is 18 cm.
I hope that this helps! Have a wonderful day!