If in ΔABC, \(\angle A+\angle B=90^\circ\) and \(\sin B=\frac{4}{5}\), then find the value of \(\cos A\).
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \(\frac{4}{5}\)
When two angles add up to \(90^\circ\), the cosine of one equals the sine of the other.
The two angles add up to \(90^\circ\): \(\angle A=90^\circ-\angle B\)
So \(\cos A=\cos(90^\circ-B)=\sin B=\frac{4}{5}\)