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Answers to Your Questions - Page 13
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Here you get answers of your CBSE mathematics 1X and X questions by our experienced teachers. To ask a question click here
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Question 130. If 3cot A=4, check whether1-tan^2 A / 1+tan^2 A = cos^2 A - sin^2 A or not by Unnikrishnan.
Answered on Feb 16, 2007 at 7:38pm I.S.T.
Answer 130.3cot A=4
                             or cot A = 4/3 = adjacent side/opposite side
                                  Let adjacent side = 4k and opposite side = 3k
                                 Hypotenuse = 5k   
                                 L.H.S. =    1-tan^2 A / 1+tan^2 A 
                                             =     [1 - (3/4)^2]/  [1 + (3/4)^2]
                                             =     [ 1 - 9/16]/[ 1 + 9/16]
                                             =     [7/16]/[25/16]
                                             =     7/16   ×   16/25  
                                             =     7/25
                                 R.H.S. =     cos^2 A - sin^2 A
                                             =     [4/5]^2 - [3/5]^2
                                             =     16/25 - 9/25
                                            =       7/25
                                  Therefore L.H.S. = R.H.S.
Question 131.A die is thrown once. Find probability of getting a composite or prime number by Parkash. Answered on Feb 17, 2008 at 8:19 pm I.S.T.
Answer 131. Favorable outcomes = 5  (2, 3, 4, 5, 6), Total outcomes = 6 (1, 2, 3, 4, 5, 6)
                                 Required Probability = Favorable outcomes/Total outcomes
                                                                      =  5/6
                                  Note - 1 is neither composite nor Prime
uestion 132. Sir, by when will the Maths (class X ) Mock test be available ? What about the answers? by Sukhman deep. Answered on Feb 23, 2008 at 1:08 a.m. I.S.T.
Answer 132. We plan to add  two Mathematics class X Mock tests with answers. One has been already added today. The answers will be added in a few days. The second mock test we plan to add in March before  Mathematics board exam.  It is available here
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Question 133.Explain why 7×11×13+13 is composite numbers by Surbhi Agarwal. Answered on Feb 25, 2007 at 11:39 pm I.S.T.
Answer 133. 7×11×13+13 
                              = 13(7×11 + 1)
                              =  13(78)
                              Now this number has more than two factors.
                              Therefore it is a composite number.
Question 134. Write the least even prime number. What are Prime numbers? by Vishnoo Prashanth. Answered on Feb 26, 2008 at 9:50 pm I.S.T.
Answer 134.The numbers which have exactly two factors are called prime numbers. These factors are 1 and the number itself.  Least and the only even prime number is 2.
Question 135.Is  [3^(1/2).x^2 + 5x -11]/[3.x^2 + 9]  a rational expression? Why? by  Surbhi Agarwal. Answered on  Feb 28, 2008 at  7:12 pm I.S.T.
Answer 135. Yes. Because it is of the form polynomial/ polynomial and denominator not equal to zero.
Question 136. I request for Social science Mock test. When can we get it because only few days are left for board exams ? by Sumati. Answered on March 1, 2008 at 1:30pm I.S.T.
Answer 136.We have already added CBSE Social Science
Mock test (full syllabus paper) yesterday. This is in addition 
to CBSE Mathematics Mock test. click here
                                   See Answers to Your questions
Question 137. What a zero of a polynomial ? by Nain Agarwal.
Answered on March 4, 2008 at 10:55pm I.S.T.
Answer 137. A real number c is said to be zero of a 
polynomial p(x) if p(c) = 0
Question 138. Prove converse of mid point theorem by basic proportionality theorem? by Nikhil Sharma. Answered on March 05 2008 at 5:19 pm I.S.T.
Answer 138. P and Q are points on sides AB and AC respectively of triangle ABC such that AP = PB and PQ II BC. By basic proportionality theorem AP/PB = AQ/QC
                                       AP/AP = AQ/QC      [since AP = PB]
                                        1 = AQ/QC
                                         AQ = QC
Statement of converse of Mid Point Theorem - A line from midpoint of one side of a triangle, parallel to second side bisects the third side.
Question 139. Define an irrational number by Ruchi Sharma.
Answered on March 6, 2008 at 7:45 pm I.S.T.
Answer 139. A real number is irrational if it cannot be represented in p/q form, where p and q are integers and q is not equal to zero
Demo: Explicit load of a +1 button