Question

in the ACD triangle picture above, if CBD = 45°, CAD = 30°, AB = 20, then BC =....​

Answer 1

Answer:

(C)10(√3 +1)

Step-by-step explanation:

let x be DC then

from fig. tan45° = DC/BC

we get DC = BC

then we get AC = 20+x

tan 30° = DC /BC

(1/√3)= (x)/(20+x)

20= x(√3-1)

x= 20/(√3 -1)

rationalize we get

x = 20(√3 +1)÷(3-1)

x = 10(√3+1)

don't know rationalizing?

Google it!