Question

In right triangle ABC in which c is the right angle prove

sin2a=(2ab)/(c^2)

Answer 1

do you know how to expand \(\sin(2a)\)?

Answer 2

yes I it 2sinacosa

Answer 3

\[\sin(2a) = 2\sin(a)\cos(a)\]

SO you have to find sina and cosa..

Answer 4

correct - now just fill-in the blanks :)

Answer 5

So would sin A be a/c?

Answer 6

yes

Answer 7

and then the proof is complete?

Answer 8

find cosa also..

Answer 9

almost - you also need cos(A)

Answer 10

cosA would be b/c

Answer 11

yes

Answer 12

just multiply sina cosa and 2..

Answer 13

now just plug those into the expansion of sin(2a)

Answer 14

2 (a/c)(b/c)

Answer 15

I get to 2(a/c)(b/c) plugging them in

Answer 16

thats it - well done! :)

Answer 17

thanks for the help

Answer 18

yw :)