It is quite embarassing that many students and visitors are posting doubts without their accurate email id. Sometimes we need some clarification in the question posted and we try to contact you via reply mail and the mail bounces back and therefore we are not able to post the answered questions at the site.
It is true that we have made it not mandatory to give us accurate email, but if there is some error in the question posted, we won’t be able to answer them until the clarifications are made.
So, please make it a point to provide the correct email id or else at least take care to post the question carefully without any typing error.
For example, We got a question “What is unit vector parpenddicular to each of the vector a=2i -j=+k and b 3i- 4j+k? calculate the sine of the angle between these vectors”. Evidently there are typing errors in it. But the question bounced when we send email for clarification.
We are getting many mails like this and we are not able to answer them. So, either be a member of the system or atleast provide your correct mail id.