Question
Sin theta equals 5/12 in quadrant, find the exact value of cos 2theta.
I'm not sure how to solve this question, I need some help.
I'm not sure how to solve this question, I need some help.
Answers
Reiny
From sinØ = 5/12
make a sketch and use Pythagoras to find the missing side x
x^2 + 5^2 = 12^2
cos 2Ø = 1 - 2 sin^2 Ø
= 1 - 2(5/12)^2
= 1 - 50/144
= 94/144
= 47/72
make a sketch and use Pythagoras to find the missing side x
x^2 + 5^2 = 12^2
cos 2Ø = 1 - 2 sin^2 Ø
= 1 - 2(5/12)^2
= 1 - 50/144
= 94/144
= 47/72
Reiny
Did not even have to find the third side, just followed my usual routine.