√53 * cosa, если ctg =3,5 и a € (Π/2; 3Π/2)

Question

√53 * cosa, если ctg =3,5 и a € (Π/2; 3Π/2)

Answer 1

1/sin²x-1=1/ctg²x
1/sin²x=1/ctg²x+1=1/3,5²+1=1 4/49=53/49
sin²x=49/53
cos²x=1-sin²x=4/53
cosx=-2/√53
√53*(-2/√53)=-2