# Sine and Cosine Laws ```Warm Up:
a) Identify the reciprocal ratios for BAT.
b) Solve for angle B.
Unit 5: Trigonometry
Day 2: Sine and Cosine Laws
Today we will.....Review the Sine and Cosine Law formulas, solve triangles using the
sine and cosine laws and solve word problems using the sine and cosine laws
The Primary Trig Ratios (SOH-CAH-TOA) only work when we
have a _____________________________ TRIANGLE.
When the triangle _______ _______ contain a right-angle we use The Sine Law
or The Cosine Law.
The Sine Law
Used when:

we know two _________ and one corresponding _____________

we know two _____________ and one ___________
The Cosine Law
Used when:

we know three ____________ and no ___________

we know two sides and their _______________ angle
Example 1:
In ΔRST, S = 40ο, T = 21ο and r = 46 cm. Find t, to the nearest centimetre.
Example 2:
In ΔPQR, P = 105.2ο, p = 23.2 cm and r = 18.5 cm. Solve the triangle.
Example 3:
Solve the following triangle. Round each angle to the nearest tenth of a degree.
Example 4:
Find the length of CD, to the nearest tenth of a metre.
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