§ 19: 19.1-19.2

19.1 Знайдіть значення виразу:

1) tg780° = tg(360° • 2 + 60°) = tg60° = 3;

2) cos(–750°) = cos750° = cos(360° • 3 + 30°) = cos30° = 32;

3) ctg225° = ctg(180° + 45°) = ctg45° = 1;

4) sin23π4 = sin(6π – π4) = sin(–π4) = –sinπ4 = –22;

5) cos7π4 = cos(2π – π3) = cos(–π4) = 22;

19.2 Знайдіть значення виразу:

tg(–325°) = –tg315° = –tg(180° • 2 – 45) = –tg(–45°) = 1;

sin1110° = sin(360° • 3 + 30°) = sin30° = 12;

cos7π3 = cos(2π + π3) = cosπ3 = 12;

sin(–9π4) = –sin9π4 = –sin(2π + π4) = –sinπ4 = –22;

ctg(–10π3) = –ctg10π3 = –ctg(3π + π3) = –ctgπ3 = –33.