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Trigonometry on BBC2 – Start date, cast, plot and everything you need to know

BBC Trigonometry
(Image credit: BBC)

A couple get an unexpected roommate in this new drama...

Trigonometry is a new love story commissioned by the BBC, and is set in "crowded and expensive London". It's now available to watch on iPlayer - see our BBC dramas 2020 guide for more top dramas to watch on iPlayer.

What is BBC series Trigonometry about?

The series follows cash-strapped couple Gemma (Thalissa Teixeira) and Kieran (Gary Carr), after they decide to open their small apartment up to a third resident.

Surprisingly, new resident Ray (Ariane Labed) seems to make things easier for the couple.

She makes the apartment feel bigger, not smaller, and the extra pair of hands makes life easier.

But they soon enter a polyamorous relationship and each resident finds themselves learning to navigate love and relationships in an entirely new way.

According to the BBC, the drama is "funny and full of sexual tension".

They add, "Trigonometry has emotional and psychological truthfulness at its heart. This is a world of consequences, in which the characters have everything to lose.

"As this unusual relationship becomes unavoidable, the trio approach it with the prudence of people in their 30s, and overthink it in a way only this generation can.

"But even when common sense, friends and family is telling them that this relationship is doomed, they simply cannot be apart."

BBC Trigonometry

Trigonometry stars Thalissa Teixeira, Araine Labed & Gary Carr. (Credit: BBC)

Who stars in BBC series Trigonometry?

The Good Fight's Gary Carr stars as Kieran, and The Musketeers' Thalissa Teixeira as his girlfriend Gemma in BBC's Trigonometry.

Completing the trio is The Lobster actress Ariane Labed as Ray, who moves in with the couple and soon becomes a love interest.

House Productions joint CEOs Tessa Ross and Juliette Howell said, “We are thrilled that Arianne, Gary and Thalissa have brought the characters in Duncan and Effie’s exquisite scripts to life in such a beautiful way”.

Actress Thalissa Teixeira added, "I'm totally overwhelmed by all of it, the scripts, the shoot, the people. I’m so happy to be a part of this exceptionally original story."

Who created the series?

Trigonometry BBC2

Trigonometry BBC2 (Image credit: BBC/House Productions/Mark Johnson)

The eight-part drama series was created by The Crown writer Duncan Macmillan and former Emmerdale actress Effie Woods.

Speaking about the project, they said, "We’re thrilled to be working with House Productions and the BBC to bring this unconventional and very adult romcom to life.

"Trigonometry is about negotiating new relationships with compassion and humour. Set in a city that can feel cold and unfriendly, at a time when we’re more divided than ever, this is a show about love.”

Trigonometry: Where can I watch it? 

All episodes are available on BBC iPlayer.


Lucy Buglass

Lucy is a digital writer with, where she writes series guides for must-watch programmes and the latest TV news. Originally from Northumberland, she graduated from Oxford Brookes University in 2016 with a degree in Film Studies and moved to London to begin a career writing about entertainment.

She is also a Rotten Tomatoes approved film critic and has a huge passion for cinema, setting up her own website Lucy Goes to Hollywood in 2017 to review films in her spare time. Her favourite genres are horror, thriller and anything crime related. When she's not writing about film and TV, you'll likely find her playing video games, reading, and trying her hand at podcasting.