Trigonometry Problems? May someone help explain how to solve these problems

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May someone help explain how to solve these problems? Thank you.

Find the number of degrees in acute angle B:
a) sin 4b = cos 5b
b) cot (2b - 30) = tan (3b + 20)
c) tan(2b = 10) = 1/cot (b+30)

a)use tri identity cos5b=sin(90-5b) and sinx-siny=2cos(x+y/2)sin(x-y/2)
simplify and get 2cos(90-x/2)sin(9x-90/2)=0
now you can do the rest

a) cos(90-4b)=cos5b so 5b=90-4b, giving b=10
b) cot(2b-30)=tan(90-2b+30)=tan(120-2b)=tan… so 120-2b=3b+20 and you can find b
c)Assume tan(2b-10) = tan(b+30) and you should be able to find b