Question

cos φ = 4/5 with 0° < φ < 90°
(a) sin 2φ

Answer 1

how do you solve this??

Answer 2

i know the answe is 24/25

Answer 3

how do you know the answer is 24/25? and what's with the a) (sin 2phi) ?

Answer 4

the a has no part in it

Answer 5

okay so do you want me to solve this algebraically or tell you how to solve it with a calulator?

Answer 6

actually i don't know if i know how to do with without a calculator lol

Answer 7

sin2phi=2sinphicosphi
we are given cosphi=4/5
then sinphi=3/5
sin2phi=2*4/5*3/5=24/25

Answer 8

cos φ = 4/5 with 0° < φ < 90°
(a) sin 2φ
lemme just use x instead of phi...
sin2x = 2sinxcosx by the double angle formula..
Look at this triangle...

this triangle is made according to the given..
So sin2x=2*(3/5)*(4/5)=24/25