Question

Given b = 12, c = 15 and A = 60° in triangle ABC, use the Law of Cosines to solve for a. Fill in the blank(s) to complete each step. Round your answer to the nearest hundredth.

a2 = --- + 152 - 2 --- (15) cos ---°

a2 = 144 + 225 - 360(---)

a2 = ---

a = ---

Answer 1

@zachleestone

Answer 2

i have to fill the --- up

Answer 3

You can use the equation
b^2 + c^2 - 2b*c*cos(60) = a^2

Answer 4

a = 16.82 right? @perl

Answer 5

not quite

Answer 6

im just bad at these stuff:(

Answer 7

357?

Answer 8

that was a typo

Answer 9

u mean?

Answer 10

I left out 15 , but i fixed it

Answer 11

oh what about a?

Answer 12

If we substitute
b = 12
c = 15
theta = 60 degrees

into the equation

b^2 + c^2 - 2ab cos (theta) = a^2

12^2 + 15^2 - 2*12*15cos(60 degrees) = a^2

144 + 225 - 2*12*15*1/2 = a^2

144 + 225 - 360*cos(60) = a^2

144 + 225 - 360 *1/2 = a^2

369 - 180 = a^2

189 = a^2

Answer 13

oh ok thnx

Answer 14

a = sqrt(189)
= sqrt( 9 * 21)
= sqrt(9)*sqrt(21)
= 3 sqrt(21)