Question

can someone help show me how this is true...
u'(t) = -sin^2(t)/cos(t) = -sect + cost

Answer 1

?

Answer 2

I don't think I understand what your asking. Are you asking does -(sint)^2/cost simplify to -sect+cost

Answer 3

yes

Answer 4

I honestly don't think it does equal

Answer 5

thats how i feel, it is in the solution manual and in order to get the same answer I need to convince myself that it is true...

Answer 6

what happens if you plug zero in on both sides? the equation doesn't hold

Answer 7

oops it does hold for t=0

Answer 8

let me think some more

Answer 9

omg im moron i got it

Answer 10

yahh!

Answer 11

okay (sint)^2+(cost)^2=1 so (sint)^2=1-(cost)^2 therefore -(sint)^2=(cost)^2-1 => -(sint)^2/cost=[(cost)^2-1]/cost

Answer 12

split those fractions up! :)

Answer 13

so we have (cost)^2/cost - 1/cost= cost-sect= -sect+cost

Answer 14

any questions? :)

Answer 15

good eye thanks!

Answer 16

sometimes im so slow

Answer 17

haha saved me a headache

Answer 18

:)