Scent intersection - help plz

[maria99]

Hi guys, I have ran out of ideas. Please help. Prove that BC/DE= cos alfa

 

[Dr.Peterson]

Scent intersection - help plz

Hi guys, I have ran out of ideas. Please help. Prove that BC/DE= cos alfaView attachment 26457

I think "scent" is supposed to be "secant".

Think about the lines and angles I've added here:

 

[maria99]

Hey yes obviously secant I am so sorry. These angle dont really give me much:/ I mean I just know that opposite angles need to give 180

 

[Dr.Peterson]

These angle dont really give me much:/ I mean I just know that opposite angles need to give 180

Please tell me what you have seen. Saying my suggestion didn't give you much doesn't help me to help you.

Do you see the relationship between the three angles? There are two very important, and very simple, facts you should see, which relate directly to the goal.

 

[maria99]

That C will have angle 90* because its on semicircle?

 

[lex]

I mean I just know that opposite angles need to give 180

You can use what you know as follows:

 

[Dr.Peterson]

That C will have angle 90* because its on semicircle?

Yes; so how are \(\alpha\) and \(\beta\) related?

Then, how are \(\beta\) and \(\gamma\) related, using another familiar theorem?