Question

Calcule o valor da expressão:
a)Sen 30 . Sen 135 + Sen 30 . Sen 360

b)Tg 180 . Tg 210 + Tg 120 . Tg 225

c )Cos π/6 . Cos 5π/π + Cos 4π/3 . Cos 5π/6

Answer 1

a) sen 30 x sen 135 x sen30 x sen 360
(1/2) x (\/2/2) x (1/2) x (0)
\/2/4 x 1/2 x 0
\/2/6 x 0
0

b)tg 180 x tg 210 x tg 120 x tg 225
(0) x (\/3/3) x (-\/3) x (1)
0 x -\/3 x 1
0 x 1
0

c)cos pi/6 x cos 5pi/6 x cos4pi/3 x cos 5pi/6
(\/3/2) x (-\/3/2) x (-1/2) x (-\/3/2)
-\/9/4 x (-1/2) x (-\/3/2)
-3/4 x (-1/2) x (-\/3/2)
3/12 x (-\/3/2)
-3\/3/24 (÷3)
-\/3/8