A community for students. Sign up today!
Here's the question you clicked on:
 0 viewing
 one year ago
Yr11 3unit question help pls!
ABC is a triangle and D is the midpoint of AC. BD=m and angle ADB = theta
(a) show that cos(theta) = 4m^2 + b^2  4c^2 / 4mb
and write an expression for cos(180theta).
(b) show a^2 +c^2 = 2m^2 + 1/2 b^2
I have done part (a) and need help on part (b) pls.
 one year ago
Yr11 3unit question help pls! ABC is a triangle and D is the midpoint of AC. BD=m and angle ADB = theta (a) show that cos(theta) = 4m^2 + b^2  4c^2 / 4mb and write an expression for cos(180theta). (b) show a^2 +c^2 = 2m^2 + 1/2 b^2 I have done part (a) and need help on part (b) pls.

This Question is Closed

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0@jim_thompson5910 @Mertsj help pls

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0umm im pretty sure ADC is 180. Why wouldnt it be?

Loser66
 one year ago
Best ResponseYou've already chosen the best response.0since I saw (theta) symbol at ADB and you indicate about ADC is theta

Loser66
 one year ago
Best ResponseYou've already chosen the best response.0ok, let tag someone who is good at geometry and trig @Mertsj

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0hmm yes i proved part a but i couldnt get part b. I think you need to do something with part a to get part b

Mertsj
 one year ago
Best ResponseYou've already chosen the best response.2\[c^2=m^2+(\frac{b}{2})^22m(\frac{b}{2})\cos \theta \]

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0ok yea i proved that part

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0and cos(180theta) is putting a negative sign infront of that equation

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0how can we prove part b though?

Mertsj
 one year ago
Best ResponseYou've already chosen the best response.2From the first part you have an expression for cos (180theta) Get another expression for cos (180theta) using triangle BCD Equate those two expressions for cos(180theta) and solve for a^2+b^2

AonZ
 one year ago
Best ResponseYou've already chosen the best response.0 4m^2 + b^2  4c^2 / 4mb = 4m^2 + b^2  4a^2 / 4mb right?
Ask your own question
Ask a QuestionFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.