C. 84
12 x 8 is the area of the whole thing but you subtract 12 because of the missing 6x2 part of the square
If cos(70) = 0.342
the cosine of the alternative angle of 70° will also give the same value
angle measure = 360 - 70 = 240°
cos (240) will also be 0.342
Answer:
54
Step-by-step explanation:
20 ÷ a + 7 • b
Let a = 4 and b = 7
20 ÷ 4 + 7 • 7
Multiply and divide first
5 + 49
Then add
54
Double-angle formulas:
2sinФcosФ=sin(2Ф) /:2
sinФcosФ=1/2*sin(2Ф)
sin(Ф/6)cos(Ф/6)=1/2*sin(2*Ф/6)=1/2*sin(Ф/3)
cos²Ф-sin²Ф=cos(2Ф)/*7
7cos²Ф-7sin²Ф=7cos(2Ф)
7cos²(Ф/9)-7sin²(Ф/9)=7cos(2*Ф/9)=7cos(2Ф/9)
