1+ctg^2a-4sin^2 a если sin^2 a=0,25

Question

1+ctg^2a-4sin^2 a если sin^2 a=0,25

Comments

1+ctg^2a = 1/sin^2a => 1/sin^2a - 4sin^2a = 1/0,25 - 4*0,25 = 4-1=3

Answer 1

Cos^2a=1-sin^2a=0.75  1+ctg^2a-4sin^2a=1+cos^2a/sin^2a-4sin^2a=1+(0.75/0.25)-4*0.25=1+3-1=3