Question

If sin A = cos 9A and 9A < 90°, then find the value of cot 10A.

Answer 1

Answer:

sinA=cos9A

sinA=cos9A ; or, sinA=sin(90°-9A)

sinA=cos9A ; or, sinA=sin(90°-9A) ; or, A=90°-9A

sinA=cos9A ; or, sinA=sin(90°-9A) ; or, A=90°-9A ; or,A+10A=90°

sinA=cos9A ;or, sinA=sin(90°-9A) ; or, A=90°-9A ; or,A+10A=90° ; or, 10A=90°

sinA=cos9A ; or, sinA=sin(90°-9A) ; or, A=90°-9A ; or,A+10A=90° ; or, 10A=90° ;or,A=9°

sinA=cos9A ; or, sinA=sin(90°-9A) ; or, A=90°-9A ; or,A+10A=90° ; or, 10A=90° ;or,A=9°Then, cot10A= cot10×9°=cot90°=0