Two angles that can be trisected with a straightedge and compass are and angles.

a.90; 30
b.90; 45
c.60; 45
d.75; 90

The correct option is B.

Step-by-step explanation:

Using the straightedge and compass we can construct the angles which are multiple of 15.

A angle can be trisected with a straightedge and compass if and only if one third of the angle is divisible by 15.

It means 30, 75 and 60 can not be trisected with a straightedge and compass. So options A, C and D are incorrect.

Two angles that can be trisected with a straightedge and compass are 90° and 45° angles. The option B is correct.

4.0 ft

step-by-step explanation:

4.0 ft

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb