Question
Download Solution PDFEvaluate the following:
cos(36° + A).cos(36° - A) + cos(54° + A).cos(54° - A)
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFGiven:
cos (36° - A) cos (36° + A) + cos (54° - A) cos (54° + A)
Formula used:
cos (a - b) = cos a cos b + sin a sin b.
sin (90 - a) = cos a
Calculation:
⇒ sin[90 – (36 – A)]sin[90 – (36 + A)] + cos (54° – A) cos (54° + A)
⇒ sin(54º + A)sin(54º – A) + cos (54° – A)cos (54° + A)
⇒ Using the identity cos(A – B),
⇒ cos(54 + A – 54 + A) = cos(2A)
Therefore, the value of cos (36° - A) cos (36° + A) + cos (54° - A) cos (54° + A) is cos(2A).
Last updated on Jun 13, 2025
-> The SSC CGL Notification 2025 has been released on 9th June 2025 on the official website at ssc.gov.in.
-> The SSC CGL exam registration process is now open and will continue till 4th July 2025, so candidates must fill out the SSC CGL Application Form 2025 before the deadline.
-> This year, the Staff Selection Commission (SSC) has announced approximately 14,582 vacancies for various Group B and C posts across government departments.
-> The SSC CGL Tier 1 exam is scheduled to take place from 13th to 30th August 2025.
-> Aspirants should visit ssc.gov.in 2025 regularly for updates and ensure timely submission of the CGL exam form.
-> Candidates can refer to the CGL syllabus for a better understanding of the exam structure and pattern.
-> The CGL Eligibility is a bachelor’s degree in any discipline.
-> Candidates selected through the SSC CGL exam will receive an attractive salary. Learn more about the SSC CGL Salary Structure.
-> Attempt SSC CGL Free English Mock Test and SSC CGL Current Affairs Mock Test.
-> Candidates should also use the SSC CGL previous year papers for a good revision.