Need help with this question quick. Pre calculus question

-56/65

sin α = 4/5 => cos α = 3/5 (because 0 < α < pi/2)

cos β = -12/13 ⇒ sin β = 5/13 (because pi/2 < β < pi)

we have:

cos(α + β) = cosα.cosβ - sinα.sinβ =

Step-by-step explanation:

50-38=12

step-by-step explanation:

c.

step-by-step explanation:

she should of added 9^2 and 12^2. that is because it is a^2+b^2=c^2. c^2 is the hypotenuse and should always be bigger than the other two numbers. which is why she should of added 9 squared and 12 squared together instead of 15 squared.