Question

calcule as expressões:
a) sen 150° - tg 300° - 4.cos 180°

b) 3.cotg 225° + cossec 210° - 2.cos 180°

Answer 1

a) sen 150° = sen 30° = +1/2
tg 300° = tg 60º = - √3
cos 180° = -1

x = sen 150° - tg 300° - 4.cos 180°
$x = - \frac{1}{2} -(- \sqrt{3} )-4(-1)$
$x = - \frac{1}{2} + \sqrt{3}+4 = \frac{7+2 \sqrt{3} }{2} = \frac{7}{2}+ \sqrt{3}$

b) cotg 225° = 1/tg 45° = 1/1 = +1
cossec 210° = 1/sen 60° = - √3/2
cos 180° = -1

y = 3.cotg 225° + cossec 210° - 2.cos 180°
$y = 3(1) + (- \frac{ \sqrt{3}}{2} ) -2(-1)$
$y = 3- \frac{ \sqrt{3}}{2}+2 = 5 - \frac{ \sqrt{3}}{2}$