Engineering

Most engineering projects are multi-disciplinary. For example, let's think about wind turbines. They are huge because the energy in the air is very diffuse and you have to intercept a lot of it to capture enough power, so they are a challenge to the structural engineer. The foundation design challenges geo-technical engineers because the turbines generate oscillating loads, and are even worse if they are offshore. The design of the blades is highly sophisticated; turbine blades are bigger than Airbus 380 wings and are complex both as aerofoil sections and as structural elements. Much more use is made of advanced fibre composites in wind turbine blades than in the aerospace industry. The gearbox design is complex because of the large forces involved, and the weight has to be kept down because they are difficult to install. The electrical generators are complex because the turbine speed varies while the national grid wants electricity at a fixed frequency. There are then complex problems about how to transmit the electricity from remote locations. You can't store electricity in significant quantities, so there is a complex control problem about matching variable demand from consumers with varying availability of wind power. Engineers do all these things, and if you look inside any piece of equipment, from mobile phones to suspension bridges, you will find interactions between many different engineering disciplines.
Engineering knows almost no bounds - we are now looking seriously at how we react to global warming. Should we aim for a world where we live with its consequences, or can we contemplate engineering the earth's climate? And if we can, should we?

Mathematics and Physics are at the heart of almost all forms of Engineering, not studied because we like an elegant proof or want to discover what happened before the Big Bang, but because we want to apply them to make a difference. So for almost all university Engineering courses a proper grounding in these subjects, with an emphasis on mechanics, is very useful.
Chemistry is certainly useful for Chemical Engineering and helps with the material science aspects of all forms of engineering, and there is also increasing overlap between Engineering and Medicine, so studying Biology as a 3rd or 4th subject is quite common.
And it's also no good being able to understand something if you can't tell people what is going on, or what you want them to do, so an ability to communicate clearly and concisely is essential if studying Engineering, and not just about using equations. You may not have to write essays as such, but you will have to write reports, and you must ensure that your meaning is clear to the reader - that is crucial if the safety of a piece of equipment depends on someone interpreting your writing.