Question

then find possible values of cos​

Answer 1

Answer:

This is in the form of quadratic equation:-

2cos2thetha-11costhetha+5=0

(roots comes out to be -10,-1)

= (2cos2 thetha-1 cos thetha)-(10cos thetha+5)=0

= cos thetha( 2cos thetha-1) -5(2cos thetha -1)=0

=(cos thetha-5)(2cos thetha-1)=0

so:-

cos thetha=5

cos thetha =1/2=60°

@AçR