Question

F +2Fcos30°+2Fcos60° solve

Answer 1

 (0°, 90°) is 0 to 90 degrees excluding0° and 90°; [0°, 90°] is 0 to 90 degrees including 0° and 90°. Acute angles are between 0° and 90° exclusive, so the answer is (a) (0°, 90°).