# The angle between two planes

**Question**

Find the angle between them the two planes below.

- Plane 1 = r.(i + 3j – 2) = 1
- Plane 2 = r.(2i + j – 3k) = 9

**Answer**

- 38.21

*Notes:*

*cos z = (Unit vector of z1)*(Unit vector of z2)*

## About the Math Tutor - Dr Loo

I am a PhD holder with 8 years of teaching experience at secondary school and university. My expertizes are mathematics, statistics, econometrics, finance and machine learning.

Currently I do provide consultation and private tuition in Singapore. For those who are looking for math tutor in Singapore or statistics tutor in Singapore, please feel free to contact me at +65-85483705 (SMS/Whatsapp/Telegram).

Some of the math tuition in Singapore I provide includes O-level math tuition and also JC Math Tuition (H1 Math Tuition & H2 Math Tuition). On the other hand, my statistics tuition in Singapore mostly focus on pre-university level until postgraduate level. For those who prefer online tutoring service, the online O-level math tuition and online JC math tuition are also available.

## For those who are looking for math tution in Singapore

Need help with this topic? I do provide mathematics home tuition in Singapore for O-level math and also JC H2 math. In addition, online math tutoring is available as well. Feel free to contact me if you would like to know further.