Prove that :

sec 40° sin 50° + cos 40° cosec 50° = 2.

If sec (90° - 3A).cos 48° = 1 and 0 ≤ 3A ≤ 90°; find the value of angle A.

If cos x = cos 40° sin 50° + sin 40° cos 50°, then find the value of angle x.