Дано
$$frac{tan^{2}{left (a + 45 right )} – 1}{tan^{2}{left (a + 45 right )} + 1}$$
Подстановка условия
$$frac{tan^{2}{left (a + 45 right )} – 1}{tan^{2}{left (a + 45 right )} + 1}$$
(tan(45 + (3))^2 – 1)/(tan(45 + (3))^2 + 1)
$$frac{tan^{2}{left ((3) + 45 right )} – 1}{tan^{2}{left ((3) + 45 right )} + 1}$$
(tan(45 + 3)^2 – 1)/(tan(45 + 3)^2 + 1)
$$frac{-1 + tan^{2}{left (3 + 45 right )}}{1 + tan^{2}{left (3 + 45 right )}}$$
(-1 + tan(48)^2)/(1 + tan(48)^2)
$$frac{-1 + tan^{2}{left (48 right )}}{1 + tan^{2}{left (48 right )}}$$
Численный ответ
(-1.0 + tan(45 + a)^2)/(1.0 + tan(45 + a)^2)
Соберем выражение
$$- cos{left (2 a + 90 right )}$$
Общий знаменатель
2
1 – —————-
2
1 + tan (45 + a)
$$1 – frac{2}{tan^{2}{left (a + 45 right )} + 1}$$
Комбинаторика
(1 + tan(45 + a))*(-1 + tan(45 + a))
————————————
2
1 + tan (45 + a)
$$frac{left(tan{left (a + 45 right )} – 1right) left(tan{left (a + 45 right )} + 1right)}{tan^{2}{left (a + 45 right )} + 1}$$
Раскрыть выражение
2
(tan(45) + tan(a))
-1 + ———————
2
(1 – tan(45)*tan(a))
————————–
2
(tan(45) + tan(a))
1 + ———————
2
(1 – tan(45)*tan(a))
$$frac{-1 + frac{left(tan{left (a right )} + tan{left (45 right )}right)^{2}}{left(- tan{left (45 right )} tan{left (a right )} + 1right)^{2}}}{1 + frac{left(tan{left (a right )} + tan{left (45 right )}right)^{2}}{left(- tan{left (45 right )} tan{left (a right )} + 1right)^{2}}}$$