It only lasts for 20 minutes, and takes 50 minutes to charge (She needs a new phone). 100-(10*5)=50
50+(20*2)=90%
she uses it for 10 minutes and charges it for 20 minutes.
So a triangle angles must add up to 180. You would subtract 180 by the two known angle which are 90 and 30. Then if you subtract them you would get 60. The final answer is 60
75+d=110 subtract 75 from both sides
d=$35
So she needs to deposit at least $35 to be able to pay the electric bill.
Hypothenus = sqrt ((x^2 - y^2)^2 + (2xy)^2) = sqrt(x^4 - 2x^2y^2 + y^4 + 4x^2y^2) = sqrt(x^4 + 2x^2y^2 + y^4) = sqrt(x^2 + y^2)^2 = x^2 + y^2