Question

найти cos B, tg B и ctg B, если sinB = 4/5

Answer 1

1)

$cos^2x + sin^2x = 1\\cos^2x = 1 - sin^2x\\cos^2x = 1 - \frac{16}{25} = \frac{9}{25} \\cos(x) = \frac{3}{5}$

2)

$tg\beta = \frac{sin\beta }{cos\beta } \\tg\beta = \frac{4}{5} : \frac{3}{5} = \frac{4 * 5}{5 * 3} =\frac{4}{3}$

3)

$ctg\beta = \frac{cos\beta }{sin\beta } \\ctg\beta = \frac{3}{5} : \frac{4}{5} = \frac{3*5}{5*4} = \frac{3}{4} = 0,75$