cosA+cos(A+B)+cos(A+2B)+cos(A+3B)+..........+cos(A+(n-1)B)=?
cosA+cos(A+B)+cos(A+2B)+cos(A+3B)+..........+cos(A+(n-1)B)=?
Aditi Dey , 7 Years ago
Grade 11
Trigonometry> cosA+cos(A+B)+cos(A+2B)+cos(A+3B)+..........
1 Answers
ayush pandey
Last Activity: 7 Years ago
Its an identity and it is equals to :(
cos(A+(n-1)B/2)×sin(nB/2) )÷sin (B÷2)
Although these questions are very rare at board level,they are useful in competetive exams and u need to practice it well to remember it at time of examination
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