Xavier Sng's answer to riz's Secondary 3 E Maths Singapore question.

done {{ upvoteCount }} Upvotes
clear {{ downvoteCount * -1 }} Downvotes
Xavier Sng
Xavier Sng's answer
801 answers (A Helpful Person)
1st
Greetings. TO is perpendicular to the triangle AOB where triangle AOB is in the same plane as the level ground. The points A, O and B are not in a straight line. Hope this helps. Regards