If there are two tangents perpendicular to each other on the function f (x) = ax + SiNx, the range of real number a is obtained But the answer is a = 0. how?

If the tangent at points (x1, f (x1)), (X2, f (x2)) is vertical, then f '(x1) = a + cosx1, f' (x2) = a + cosx2f '(x1) f' (x2) = (a + cosx2) (a + cosx2) = - 1A ^ 2 + (cosx1 + cosx2) a + (cosx2cosx2 + 1) = 0 (*) because the value of a must exist, that is, the equation (*) must have a solution, so the discriminant

If there are two tangents perpendicular to each other on the function f (x) = ax + SiNx, the range of real number a is obtained But the answer is a = 0. how?

If there are two tangents perpendicular to each other on the function f (x) = ax + SiNx, the range of real number a is obtained But the answer is a = 0. how?

RELATED INFORMATIONS