A year ago, I posted this problem on [MSE]. Now I have edit  the following similar problem.(To adopt Hjalmar Rosengren suggestion)

 

 Which rarional values of $c$ and $d$,the numbers
$\sin{(\pi\cdot c)},\sin{(\pi\cdot d)}$ and $1$ are linearly dependent over $Q$

**Question 1:** 
case 1:
when $d=\dfrac{1}{18}$,How prove this $c=\dfrac{1}{18}?$

**Question 2** 
case 2: when $d\in Q$ give numbers,I guess also $c=d?$

because the case $d=0$ is known as [Niven's Theorem]




[Niven's Theorem]:http://mathworld.wolfram.com/NivensTheorem.html