Prove that sin alpha × sin(90- alpha) - cos(90-alpha) × cos alpha

It is equal to 0.

Step-by-step explanation:

I can simplify it as follows:

sinα sin(90 - α) - cos(90 - α)(cosα)

Now  sin(90 -α) = cosα and cos(90 - α) = sinα)    ( for α < 90)

So the expression becomes:

sinαcosα - sinαcosα

= 0 .

let y equal to

the total fare and x is the mile of taxi ride. so the equation is

y = 0.55x + 1.75

since susie has

$10 to spend for a taxi cab, so he can have

10 = 0.55x +

1.75

x = 15 miles of

taxi ride

so the system of

inequality is

10 < 0.55x +

1.75

x > 2