Sine rule and cosine rule Quiz

1. In triangle $ABC$, $A=30^\circ$, $B=45^\circ$ and $a=8$. Find $b$.

• A. $5.66$
• B. $11.3$
• C. $9.80$
• D. $16.0$

2. In a triangle, $a=5$, $b=7$ and $C=60^\circ$. Find $c$.

• A. $\sqrt{74}$
• B. $\sqrt{109}$
• C. $39$
• D. $\sqrt{39}$

3. Two sides and the included angle are known. Which rule finds the third side?

• A. The cosine rule
• B. The sine rule
• C. The tangent ratio
• D. Pythagoras' theorem only

4. Find the largest angle of a triangle with sides 5, 6 and 7.

• A. $44.4^\circ$
• B. $57.1^\circ$
• C. $78.5^\circ$
• D. $101.5^\circ$

5. In triangle $ABC$, $\cos B=-0.25$. What kind of angle is $B$?

• A. Acute, less than $45^\circ$
• B. Obtuse
• C. A right angle
• D. Impossible in a triangle