Question

4cos2a+2cosa+3=0 find the value of cosa​

Answer 1

Step-by-step explanation:

cos2a = 2cos^2 a - 1

4(2cos^2 a - 1) +2cosa +3 =0

8 cos^2 a + 2 cos a -1 (put cos a = x)

then 8x^2 + 2x -1 =0 from solving middle term spitting we get, cos a= 1/4 or -1/2.