# Trigonometric identity

Hi, please could i have help on this question? I divided both sides by tan theta and got cos theta=1/2 and found the solutions but the markscheme also has sin thet=0 but I don’t get where that came from?
Here is the question; https://app.gemoo.com/share/image-annotation/592087963147464704?codeId=M0G6nRA2V4VRY&origin=imageurlgenerator

Here is the markscheme: https://app.gemoo.com/share/image-annotation/592088707225399296?codeId=M0G6nndgLWBlg&origin=imageurlgenerator

Thank you!
Original post by anonymous294
Hi, please could i have help on this question? I divided both sides by tan theta and got cos theta=1/2 and found the solutions but the markscheme also has sin thet=0 but I don’t get where that came from?
Here is the question; https://app.gemoo.com/share/image-annotation/592087963147464704?codeId=M0G6nRA2V4VRY&origin=imageurlgenerator

Here is the markscheme: https://app.gemoo.com/share/image-annotation/592088707225399296?codeId=M0G6nndgLWBlg&origin=imageurlgenerator

Thank you!

You divided out the extra solution. So factorise tan(theta) and reason about the values of each factor.
Original post by mqb2766
You divided out the extra solution. So factorise tan(theta) and reason about the values of each factor.

That makes sense, thank you!