Question

Please help me do this step by step

Answer 1

Answer:

=> 3sin²x - 8cosx - 7 = 0

=> 3 - 3cos²x - 8cosx - 7 = 0

=> -3cos²x - 8cosx - 4 = 0

=> 3cos²x + 8cosx + 4 = 0

=> 3cos²x + 6cosx + 2cosx + 4 = 0

=> (3cosx+2)(cosx+2) = 0

=> cosx = -2 not possible

so that cosx = -2/3

=> cos(@+70) = -2/3

=> @+70 = cos^-1(-2/3)

=> @+70 = 131

=> @ = 61 degree

Answer 2

Answer:

$= \ > \: 3 \sin ^{2} x - 8 \cos \: x \: - 7 = 0 \\ = > 3 - 3 \cos^{2} x8 \cos \: x - 7 = 0 \\ = > - 3 \cos ^{2}x - 8 \cos \: x - 4 = 0 \\ = > 3 \cos ^{2} x - 8 \cos \: x - 4 \ = 0 \\ = > 3 \cos ^{2} + 6 \cos \: x + 2 \cos \: x + 4 = 0 \\ = > (3 \cos \: x + 2 )(cos + 2) = 0 \\ = > \cos = - 2 \: will \: be \: not \: possible \\ \\ \\ = > so \: that \: \cos \: x = - 2 |3 \\ \ = > cos \: \alpha + 70 = - 23 \\ = > \alpha \: + 70 = \cos \: - 1( \: - 2 | \: 3) \\ = > \alpha + 70 = 131 \\ = > \alpha = 61 \: degrees$