sin(90+a)-cos(a-90)^2*1/sin(a+270) если a=1/3 (упростите выражение)

$$sin{left (a + 90 right )} – frac{cos^{2}{left (a – 90 right )}}{sin{left (a + 270 right )}}$$

$$sin{left (a + 90 right )} – frac{cos^{2}{left (a – 90 right )}}{sin{left (a + 270 right )}}$$

sin(90 + (1/3)) – cos((1/3) – 90)^2/sin((1/3) + 270)

$$sin{left ((1/3) + 90 right )} – frac{cos^{2}{left ((1/3) – 90 right )}}{sin{left ((1/3) + 270 right )}}$$

sin(90 + 1/3) – cos(1/3 – 90)^2/sin(1/3 + 270)

$$- frac{cos^{2}{left (-90 + frac{1}{3} right )}}{sin{left (frac{1}{3} + 270 right )}} + sin{left (frac{1}{3} + 90 right )}$$

-cos(269/3)^2/sin(811/3) + sin(271/3)

$$- frac{cos^{2}{left (frac{269}{3} right )}}{sin{left (frac{811}{3} right )}} + sin{left (frac{271}{3} right )}$$

-cos(a – 90)^2/sin(a + 270) + sin(90 + a)

$$frac{1}{sin{left (a + 270 right )}} left(sin{left (a + 90 right )} sin{left (a + 270 right )} – cos^{2}{left (a – 90 right )}right)$$

$$frac{1}{sin{left (a + 270 right )}} left(sin{left (a + 90 right )} sin{left (a + 270 right )} – cos^{2}{left (a – 90 right )}right)$$

$$- left(frac{1}{2} cos{left (2 a – 180 right )} + frac{1}{2}right) csc{left (a + 270 right )} + sin{left (a + 90 right )}$$

/ 2
-cos (-90 + a) – sin(90 + a)*sin(270 + a)/
——————————————–
sin(270 + a)

$$- frac{1}{sin{left (a + 270 right )}} left(- sin{left (a + 90 right )} sin{left (a + 270 right )} + cos^{2}{left (a – 90 right )}right)$$

2
(cos(90)*cos(a) + sin(90)*sin(a))
cos(90)*sin(a) + cos(a)*sin(90) – ———————————-
cos(270)*sin(a) + cos(a)*sin(270)

$$- frac{left(sin{left (90 right )} sin{left (a right )} + cos{left (90 right )} cos{left (a right )}right)^{2}}{sin{left (a right )} cos{left (270 right )} + sin{left (270 right )} cos{left (a right )}} + sin{left (a right )} cos{left (90 right )} + sin{left (90 right )} cos{left (a right )}$$