- 4 1/5 = -21/5 = -42/10
-13 1/10 = -131/10
-42/10 - -131/10=
-42/10 + 131/10 = 89/10 = 8 9/10
answer is A
I don't know if this will help but the 2 on the right are not parallelograms there
"3d"
Step-by-step explanation:
1. AB = BC (B is the midpoint of AC)
2. DE = EF (E is the midpoint of DF)
3. EB is common
4. ∠ABE = ∠CBE; ∠BED = ∠BEF (EB⊥AC, EB⊥DF)
5. ΔDEB ≅ ΔFEB (RHS)
6. DB = FB (corresponding ∠s of ≅ Δs)
7. ∠EFB = ∠CBF; ∠EDB = ∠ABD (alternate interior angles, AC║DF)
8. ΔABD ≅ ΔCBF (SAS)
Answer:
204/325
Step-by-step explanation:
You can work this a couple of ways. We expect you are probably expected to use trig identities.
cos(A) = √(1 -sin²(A)) = 24/25
sin(B) = √(1 -cos²(B)) = 12/13
cos(A -B) = cos(A)cos(B) +sin(A)sin(B) = (24/25)(5/13) +(7/25)(12/13)
= (24·5 +7·12)/325
cos(A -B) = 204/325
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The other way to work this is using inverse trig functions. It is necessary to carry the full calculator precision if you want an exact answer.
cos(A -B) = cos(arcsin(7/25) -arccos(5/13)) = cos(16.2602° -67.3801°)
= cos(-51.1199°) ≈ 0.62769230 . . . . (last 6 digits repeating)
The denominators of 25 and 13 suggest that the desired fraction will have a denominator of 25·13 = 325, so we can multiply this value by 325 to see what we get.
325·cos(A-B) = 204
so, the exact value is ...
cos(A -B) = 204/325
