two tangents are drawn from the point (-2,-1) to a parabola. if thita is the angle between them, what is the value of tan thita

3 years ago


Answers : (2)


Hi Rupali,


You've not mentioned the equation of the parabola. (Assuming it as y^2 = 4x)


The eqn of any tangent to a parabola y^2 = 4ax is y = mx+a/m


So the equation of any tangent to this parabola, would be y=mx+1/m (as a=1, for y^2=4x)

Now these tangents pass through (-2,-1)... so -1=-2m+1/m

Or 2m2-m-1=0.

Where m1,m2 are the slopes of the two tangents that satisfy this equation (m1,m2 are the roots of the quad)....


So tan(angle between the tangents) = |(m1-m2)/(1+m1m2)|

Now m1m2 = -1/2

And m1-m2 = root { (m1+m2)2-4m1m2 } = root [ (1/2)2 - 4(-1/2) ] = root[9/4].

So |m1-m2| = 3/2.


Hence tan(Angle) = (3/2) / (1/2) = 3.....


And that is the answer.


Best Regards,

Ashwin (IIT Madras).

3 years ago

You have to give the equation of parabola.

3 years ago

Post Your Answer

More Questions On IIT JEE Entrance Exam

Ask Experts

Have any Question? Ask Experts
Post Question
Answer ‘n’ Earn
Attractive Gift
To Win!!!
Click Here for details
how many marks i have to score in jee advanced to qualyfie for iit bombay mach. engg. in ge category..???? GENREL
IIT Bombay Mechanical Engineering 2013 Opening Rank:24Closing Rank: 477 (GE) Hence, taking into consideration a minor shift in the opening and closing ranks for 2014, its safe to say that...
Aziz Alam 3 months ago
Dear sir , i got seat in iiit hyderabad and iit hyderabad, cse branch in both colleges which is better?
IIIT CSE Hyderabad is better than IIT CSE Hyderabad. IIIT CSE Hyderabad is one of the reputed branches in all over India. CSE of IIIT Hyderabad is even better than CSE of many IITs. [The...
Aziz Alam 3 months ago
iam in a strong will to clear IIT JEE 2015....can you please suggest me some preparation tips.....
Preparing forIIT-JEE is surely a difficult thing but it all depends on how you manage your time. The key for this planning is to first set some long-term goals and then set up short-term...
Saurabh Kumar 4 days ago
Hi, The best thing is to make a study schedule and follow it strictly. Keep a balance between theory and numericals and follow good books instead of completing many books. thanks...
Shobhit Varshney 4 days ago
how to balance between the studies for iit-jee and other all exams with it
Dear Shweta, Syllabus of IIT-JEE is more or less the same as other entrance exams. Other exams like AIEEE, BITSAT include several extra chapters to the IIT JEE syllabus. So if your...
Askiitians Expert Himanshu Geed - IIT Delhi 4 years ago
Dear shweta To balance between IIT JEE and all other exam ,you need not to make extra effort.because almost all the exam have same syllabus.only in few exam you will see few more chapters....
Badiuddin askIITians.ismu Expert 4 years ago
Hi.. I am little bit confuse that i should target Computer programming courses or should go in Technical degree programmes. I have interest in programming. So please give me guidance for my...
Hi I would suggest u to go for Technical courses , as there is ample of computer programming involved in technical courses like computer , IT , ECE engineering and also they have gt a much...
AskiitianExpert Shine 5 years ago
what is the rank required to do chemical at iit bombay
Hello, last year the rank is between 222 and 1040AIR for chemical at IITB regards Ramesh
Ramesh V 5 years ago
up to AIR 1200 u can get Chemical at IIT Bombay
Badiuddin askIITians.ismu Expert 5 years ago
View all Questions »