Hello,

Although I feel capable enough to solve this, for some reason my answer is quite different than the actual answer to the point that I wonder if the official answer could be wrong.



Consider circle c with line BD through the center of the circle A and with B and D on c. Consider point D so that BD = 2, ∟DBC = 15 degrees and ∟DCB = 45 degrees. What is the area of circle c?

Attempt:


According to the official answer, the area equals 3/2 * Pi. I cannot for the life of me find what I've done wrong and am considering the possibility that I am not at fault ._.

The use of the sine rule clearly leads to 3/2 Pi, so I guess I found the correct answer. I'd still like to know why it is that my attempt is flawed
/e Because sin(15) does not equal a half. Close topic ^^

This post was edited by Forg0tten on Jun 29 2017 04:27pm

Angle for DBC would have to be 30 for it to work out as you said.

The wording of the problem is fairly vague though. Is the point C supposed to be the center of the circle c? If so I'm not sure it would be possible for DCB to be 45 while DBC is 15 if D and B both appear on the circle c. I could be misunderstanding what the point C is in relation to the circle c though.

Huh, I might've wrote it up wrongly.

Consider circle c with center A. There is a line BD where B and D are on the circle, that goes through the middle (it divides the circle in half). Then, there's a third point that I apparently called D again (but is actually C in my attempt), that's basically "floating" in one of the circle halves. BDC form a triangle, where BC equals 2. The angles are given.

Solved using the difference formula for cos(15)=cos(60-45).
/Close