I just tried your code and it worked for me, so you must not have your variables defined.
Can you console.log your $scope.params.workgroupId and $scope.params.reportedOn variables right before your $http.get. I'm betting that they are undefined. I just put the following into one of my programs (removed the .params just for convenience; unless you're thinking that's needed for some reason?) and added the $http dependency in my controller and it worked just fine.
$scope.workgroupId = 1;
$scope.reportedOn = 2;
$http.get("/api/v1/entries", {params: {workgroupId:$scope.workgroupId, reportedOn:$scope.reportedOn}});