Question

sin3A = cos(A-26) where A is an acute angle. Find the value of A

Answer 1

here...sin3A becomes cos(90-3A).and so....A-26=90-3A.so..........4A=90+26......so....A=26..........& THIS IS YOUR ANS........

Answer 2

Answer:

$Given, \: \sin(3A) = \cos(A - {26}^{o} ) \: \: \: \: \: \: ...........(i) \\ where, \: 3A \: is \: an \: acute \: angle. \\ We \: know \: that, \: \: sin ϑ  = cos( {90}^{o} -  ϑ ) \\ From \: Eq. \: (i), \: cos( {90}^{o} - 3A) = cos(A - 26) \\ Since, \: ( {90}^{o} - 3A) \: and \: (A - {26}^{o} ) \: both \: are \: acute \: angles. \\ ∴ \: {90}^{o} -3A = A - {26}^{o} \\ ➪ \: 4A = {116}^{o} \\ ➪ \: A = \frac{ {116}^{o} }{4} \\ ➪ \: A = {29}^{o}$