英文文法，為何用in strengthening 而不是to strengthen ?

To promote our arts and cultural development and in tandem with the progress of the West Kowloon Cultural District,
we would continue to invest resources and adopt a multi-pronged approach 「in strengthening our cultural 」software through arts program development, manpower training, promotion of arts education and audience building.
為了推動本地的文化發展和配合西九文化區的建設，我們會持續投放資源，透過 多管齊 下 的方針， 即發 展藝術 節目、培育人才、推動藝術教育，以及拓展觀眾， 進一步強化我們的文化軟件。

為何是 in strengthening our cultural
而不是 to strengthen our cultural...
為何？要這樣用？