5.12. Wykaż, że: a tg5^ * tg25^ * tg45^ * tg65^ * tg85^ =1 b) cos^2 (20 degrees) + cos^2 (40 degrees) + cos^2 (50 degrees) + cos^2 (70 degrees) = 2 =) sin^4 (20 degrees) + sin^4 (70 degrees) + 2cos^2 (20 degrees) * cos^2 (70 degrees) = 1 . ctg * alpha = 4 , to , 32* sin a-sin(90^ – alpha) 6* cos(90^ – alpha)+2* cos alpha =2 5

 5.12. Wykaż, że: a tg5^ * tg25^ * tg45^ * tg65^ * tg85^ =1 b) cos^2 (20 degrees) + cos^2 (40 degrees) + cos^2 (50 degrees) + cos^2 (70 degrees) = 2 =) sin^4 (20 degrees) + sin^4 (70 degrees) + 2cos^2 (20 degrees) * cos^2 (70 degrees) = 1 . ctg * alpha = 4 , to , 32* sin a-sin(90^ – alpha) 6* cos(90^ – alpha)+2* cos alpha =2 5