In the triangle below, the length of side a is 10 and the length of side b is 12. Given that the value of cos(theta) is equal to 1/5 find the value of cos(delta)?

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Answer 1 · 2017-12-31T22:03:47

#cosbeta=19/35#

.

#a=10# and #b=12#

From laws of cosines, we have:

#c^2=a^2+b^2-2abcosgamma#

#c^2=100+144-2(10)(12)(1/5)=196#

#c=sqrt196=14#

#b^2=a^2+c^2-2accosbeta#

#144=100+196-2(10)(14)cosbeta#

#280cosbeta=152#

#cosbeta=152/280=19/35#