PROGRAM TRIANG
      COMMON/TRIANGLE/A,ANGLEA,ANGLEB
      COMMON/CALCULATION/ANGLEC,MINANGLE
      COMMON/FORCHECK/FLAG
      CALL FUNCTION
      END

      SUBROUTINE FUNCTION
      INTEGER NUMBER
      PRINT*, 'PLEASE, USE THE INSTRUCTIONS:'
      PRINT*, 'TYPE "1" FOR CREATING A NEW TRIANGLE'
      PRINT*, 'TYPE "2" FOR CALCULATION OF THE AREA OF THE TRIANGLE'
      PRINT*, 'TYPE "3" FOR CALCULATION OF THE MIN ANGLE'
      PRINT*, 'TYPE "4" FOR CALCULATION OF THE COSINUS OF THE MIN ANGLE'
      PRINT*, 'TYPE "5" FOR EXIT'
      READ*, NUMBER
      IF(NUMBER.EQ.1) CALL CREATE
      IF(NUMBER.EQ.2) CALL AREATRIANGLE
      IF(NUMBER.EQ.3) CALL MIN
      IF(NUMBER.EQ.4) CALL COSMIN
      IF(NUMBER.EQ.5) RETURN
      CALL FUNCTION
      END

      SUBROUTINE CREATE
      COMMON/TRIANGLE/A,ANGLEA,ANGLEB
      COMMON/FORCHECK/FLAG
      PRINT*, 'TYPE THE SIDE OF THE TRIANGLE'
      READ*,A
      PRINT*, 'TYPE THE NEIGHBOR ANGLE'
      READ*,ANGLEA
      PRINT*, 'TYPE THE OPPOSITE ANGLE'
      READ*,ANGLEB
      CALL FINDERR
      IF(FLAG.EQ.1)THEN
      RETURN
      ELSE
      PRINT*,'YOU TYPED ',A,ANGLEA,ANGLEB
      ENDIF
      END

      SUBROUTINE AREATRIANGLE
      COMMON/TRIANGLE/A,ANGLEA,ANGLEB
      COMMON/CALCULATION/ANGLEC,MINANGLE
      COMMON/FORCHECK/FLAG
      REAL*4 SQ
      IF(FLAG.EQ.1)RETURN
      CALL CALCULMIN
      SQ=A**2/2*SIN(ANGLEA)*SIN(ANGLEB)/SIN(ANGLEC)
      SQ=ABS(SQ)
      PRINT*,'THE AREA OF THE TRIANGLE IS ',SQ
      END

      SUBROUTINE MIN
      COMMON/CALCULATION/ANGLEC,MINANGLE
      COMMON/FORCHECK/FLAG
      IF(FLAG.EQ.1)RETURN
      CALL CALCULMIN
      PRINT*,'THE MIN ANGLE IS ',MINANGLE
      END

      SUBROUTINE CALCULMIN
      COMMON/TRIANGLE/A,ANGLEA,ANGLEB
      COMMON/CALCULATION/ANGLEC,MINANGLE
      ANGLEC=180-ANGLEA-ANGLEB
      IF(ANGLEA.LE.ANGLEB)THEN
      MINANGLE=ANGLEA
      ELSE
      MINANGLE=ANGLEB
      ENDIF
      IF(ANGLEC.LE.MINANGLE)THEN
      MINANGLE=ANGLEC
      ENDIF
      END

      SUBROUTINE COSMIN
      COMMON/CALCULATION/ANGLEC,MINANGLE
      COMMON/FORCHECK/FLAG
      REAL*4 COSMINANG
      IF(FLAG.EQ.1)RETURN
      CALL CALCULMIN
      COSMINANG=MINANGLE
      PRINT*, 'THE COSINUS OF THE MIN ANGLE IS ',COS(COSMINANG)
      RETURN
      END


      SUBROUTINE FINDERR
      COMMON/FORCHECK/FLAG
      CALL CHECK
      IF(FLAG.EQ.1)CALL ERROR
      RETURN
      END

      SUBROUTINE CHECK
      COMMON/TRIANGLE/A,ANGLEA,ANGLEB
      COMMON/FORCHECK/FLAG
      IF(ANGLEA.LE.0.OR.ANGLEA.GE.180)THEN
      FLAG=1
      RETURN
      ENDIF
      IF(ANGLEB.LE.0.OR.ANGLEB.GE.180)THEN
      FLAG=1
      RETURN
      ENDIF
      IF(ANGLEA+ANGLEB.GE.180)THEN
      FLAG=1
      RETURN
      ENDIF
      IF(A.LE.0)THEN
      FLAG=1
      RETURN
      ENDIF
      FLAG=0
      RETURN
      END

      SUBROUTINE ERROR
      PRINT*, 'WRONG DATA, PLEASE, CHECK THE STATES'
      RETURN
      END