1.

If A is an acute angle and cot A + cosec A = 3, then the value of cos A is equal to:1. 4/52. 3/53. 1/54. 2/5

Answer» Correct Answer - Option 1 : 4/5

Given: 

cot A + cosec A = 3

Formula used :

cosec2 A - cot2 A = 1

cosec A - cot A   = 1/ ( cosec A + cot A)

cot A + cosec A = 3     ......(eq1)

cosec A - cot A  =1/3   .......(eq2) 

By solving eq 1 and eq 2 By elimination

2 cosec A = 3 + 1/3

cosec A = 5/3 = H / P

 \({H^2} = {P^2} + {B^2}\)

\({5^2} = {3^2} + {B^2}\)

B2 = 25 - 9

B= 16

base = 4

cosA = 4/5



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