Cambridge Trig (1 Viewer)

[kazemagic]

O_O I need help with question 8,b) in Cambridge

I can't prove QR=asinB cos^2B
The closest proving I got was (2acos^2B)/sinB

Any help would be appreciated! Thanks

 

[kazemagic]

Got another question...

How do I prove POC=2 theta- any hints?

Thanks

 

[deswa1]

Method 1: Use circle geometry-> Angle subtended by a chord at the centre is twice the angle subtended at the circumference.
Method 2: Angle OCA = theta as triangle OCA is isoceles. Therefore angle POC= 2x theta (exterior angle of a triangle)
Method 3: Angle ACB= 90 degrees (angle in a semicircle). Therefore angle CBA=90-theta (angle sum of triangle). Angle OCB also equals 90-theta (triangle OBC is isoceles). Therefore angle POC = 2x theta (angle sum of triangle)

 

[kazemagic]

Thanks, you mean the triangle above is a right angle one right? Yea got that. I proved PCB but trying to figure out POC
omg! thx! I totally forgot about the radii lol

 

[delian]

Thanks, you mean the triangle above is a right angle one right? Yea got that. I proved PCB but trying to figure out POC
omg! thx! I totally forgot about the radii lol

Don't worry. sometimes you can't figure it out for a long time.

 

[kazemagic]

Don't worry. sometimes you can't figure it out for a long time.

Quite relieving to hear that