# CAT Quantitative Aptitude Questions | Geometry Questions for CAT - Trigonometry

###### CAT Questions | CAT Trigonometry Questions | Trigonometric Identities
CAT Questions

The question is from CAT Geometry - Trigonometry. This is about Trigonometric Identities. Our task is to find out the value of the term which is in a, b, c, d. Trigonometry is an important topic for CAT Preparation for the CAT Exam. Trigonometric ideas can be completely opposite, as in, some questions test lot of common sense with direction, heights and distances, while others could test you on identities. CAT exam could test one on both these fronts. Make sure you master both in CAT - Trigonometry.

Question 5: : If cos A + cos2 A = 1 and a sin12 A + b sin10 A + c sin8 A + d sin6 A - 1 = 0. Find the value of a+b/c+d

1. 4
2. 3
3. 6
4. 1

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##### Method of solving this CAT Question from CAT Geometry - Trigonometry : Can we use pythagorean triplets here? Think!!

Given,
Cos A = 1 - Cos2A
=> Cos A = Sin2 A
=> Cos2A = Sin4A
=> 1 – Sin2 A = Sin4 A
=> 1 = Sin4 A + Sin2 A
=> 13 = (Sin4A + Sin2A)3

=> 1 = Sin12 A + Sin6A + 3Sin8 A + 3Sin10 A
=> Sin12 A + Sin6A + 3Sin8 A + 3Sin10 A – 1 = 0

On comparing,
a = 1, b = 3 , c = 3 , d = 1
∴ $$frac{b}{c}\\$ + d = 3 Always look out for Pythagorean triplets, we know that$8,15,17) is one
∴ 17 ($$frac{18}{7}\\$CosA+$\frac{15}{17}\\$SinA) The question is "Find the value of a+b/c+d" ##### Hence, the answer is 3 Choice B is the correct answer. ###### Best Online CAT CoachingSignup and sample5 classes for free Signup Now! ###### Already have an Account? ###### CAT Coaching in ChennaiEnroll at 29000/- Next Weekend Batch Starts Sat, June 29th, 2019 ###### Best CAT Coaching in ChennaiEarly Bird discount of 7000 Personalised attention, Small batch sizes. ## CAT Preparation Online | CAT Geometry - Trigonometry Videos On YouTube #### Other useful sources for Geometry Questions | Trigonometry Questions ##### Where is 2IIM located? 2IIM Online CAT Coaching A Fermat Education Initiative, 10-C, Kalinga Colony, Bobbili Raja Salai K.K.Nagar, Chennai. India. Pin - 600 078 ##### How to reach 2IIM? Phone:$91) 44 4505 8484
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