The paper contains a letter that al-Biruni wrote to al-Sijzi (translated into English in) which contains proofs of both the plane and spherical versions of the sine theorem.
Ang papel ay naglalaman ng isang sulat na al-Biruni wrote sa al-Sijzi (isinalin sa Ingles) na naglalaman ng proofs ng parehong ang eroplano at pabilog na bersyon ng sain teorama.